US forces helping to evacuate Afghans desperate to flee Taliban rule are on alert for more attacks after at least one Islamic State suicide bomber killed 85 people including 13 US soldiers outside the gates of Kabul airport.

Two blasts and gunfire rocked the area outside the airport on Thursday evening, witnesses said. Video shot by Afghan journalists showed dozens of bodies strewn around a canal on the edge of the airport.

A health official and a Taliban official said the toll of Afghans killed had risen to 72, including 28 Taliban members, although a Taliban spokesman later denied that any of their fighters guarding the airport perimeter had been killed.

The US military said 13 of its service members were killed and 18 wounded in what it described as a complex attack.

Islamic State (ISIS), an enemy of the Islamist Taliban as well as the West, said one of its suicide bombers targeted "translators and collaborators with the American army".

It was not clear if suicide bombers detonated both blasts or if one was a planted bomb. It was also not clear if ISIS gunmen were involved in the attack or if the firing that followed the blasts was Taliban guards firing into the air to control crowds.

General Frank McKenzie, head of US Central Command, said US commanders were watching for more attacks by Islamic State, including possibly rockets or car bombs targeting the airport.

"We're doing everything we can to be prepared," he said, adding that some intelligence was being shared with the Taliban and that he believed "some attacks have been thwarted by them."

US forces are racing to complete their withdrawal from Afghanistan by an August 31 deadline set by President Joe Biden.

He says the United States long ago achieved its original rationale for invading the country in 2001: to root out al Qaeda militants and prevent a repeat of the September 11 attacks on the United States that year.

Biden said he had ordered the Pentagon to plan how to strike ISIS-K, the Islamic State affiliate that claimed responsibility.

"We will not forgive. We will not forget. We will hunt you down and make you pay," Biden said during televised comments from the White House.

Video of the attack showed corpses in a waste water canal by the airport fence, some being fished out and laid in heaps while wailing civilians searched for loved ones.

"I saw bodies and body parts flying in the air like a tornado blowing plastic bags," said one Afghan witness. "That little water flowing in the sewage canal had turned into blood."

British Defence Secretary Ben Wallace said the threat of attacks would increase as Western troops got closer to completing the huge airlift and leaving.

"The narrative is always going to be, as we leave, certain groups such as ISIS will want to stake a claim that they have driven out the US or the UK," Wallace told Sky News.

ISIS-K was initially confined to areas on the border with Pakistan but has established a second front in the north of the country. The Combating Terrorism Centre at West Point says ISIS-K includes Pakistanis from other militant groups and Uzbek extremists in addition to Afghans.

Western countries fear the Taliban, who once sheltered Osama bin Laden's al Qaeda before it was ousted from power by the US-led 2001 invasion, will allow Afghanistan to turn again into a haven for militants. The Taliban say they will not let the country be used by terrorists.

The US will press on with evacuations despite the threat of further attacks, McKenzie said, noting there were still about 1000 US citizens in Afghanistan.

In the past 12 days, Western countries have airlifted nearly 100,000 people. But they acknowledge that thousands will be left behind when the last US troops leave at the end of the month.

Worries are growing that the remaining population will face a humanitarian crisis with the coronavirus spreading and shortages of food and medical supplies looming.

The World Health Organisation said it hoped to establish an air bridge into the northern city of Mazar-i-Sharif with the help of Pakistani authorities to get medical supplies in.

© RAW 2021

US forces helping to evacuate Afghans desperate to flee Taliban rule are bracing for more attacks after an Islamic State suicide bomber killed scores of civilians and 13 US soldiers outside the gates of Kabul airport.

Kabul health officials were quoted as saying 60 civilians were killed in the attacks on Thursday. At least two blasts and gunfire rocked the area, witnesses said.

Video shot by Afghan journalists showed dozens of bodies strewn around a canal on the edge of the airport.

Islamic State (ISIS), an enemy of the Taliban as well as the West, said one of its suicide bombers targeted "translators and collaborators with the American army".

US officials also blamed the group and vowed retribution.

General Frank McKenzie, head of US Central Command, said US commanders were on alert for more attacks by Islamic State, including possibly rockets or vehicle-borne bombs targeting the airport.

"We're doing everything we can to be prepared," he said, adding that some intelligence was being shared with the Taliban and that he believed "some attacks have been thwarted by them".

US forces are racing to complete their withdrawal from Afghanistan by an August 31 deadline set by President Joe Biden, who said the US had long ago achieved its original rationale for invading the country in 2001: to root out al Qaeda militants and prevent a repeat of the September 11 attacks on the United States.

Biden said he had ordered the Pentagon to plan how to strike ISIS-K, the Islamic State affiliate that claimed responsibility.

"We will not forgive. We will not forget. We will hunt you down and make you pay," Biden said during televised comments from the White House on Thursday.

Video taken in the aftermath of the attack showed corpses in a sewage canal by the airport fence, some being fished out and laid in heaps while wailing civilians searched for loved ones.

"I saw bodies and body parts flying in the air like a tornado blowing plastic bags," said one Afghan witness.

"That little water flowing in the sewage canal had turned into blood."

Zubair, a 24 year-old civil engineer, said he was close to a suicide bomber who detonated explosives.

"Men, women and children were screaming. I saw many injured people - men, women and children - being loaded into private vehicles and taken toward the hospitals," he said.

A US Central Command spokesman said 18 soldiers injured in the attack were "in the process of being evacuated from Afghanistan on specially equipped C-17s with embarked surgical units".

A Taliban official said at least 28 members of the militant group were killed in the attack.

"We have lost more people than the Americans in the airport blast," he said, adding the Taliban was "not responsible for the chaotic evacuation plan prepared by foreign nations".

Western countries fear that the Taliban, who once sheltered Osama bin Laden's al Qaeda, will allow Afghanistan to turn again into a haven for militants. The Taliban say they will not let the country be used by terrorists.

ISIS-K was initially confined to areas on the border with Pakistan but has established a second front in the north of the country. The Combating Terrorism Center at West Point said ISIS-K includes Pakistanis from other militant groups and Uzbek extremists in addition to Afghans.

The US would press on with evacuations despite the threat of further attacks, McKenzie said, noting that there were still about 1000 US citizens in Afghanistan.

The pace of evacuation flights had accelerated on Friday and American passport holders had been allowed to enter the airport compound, said a Western security official stationed inside the airport.

In the past 12 days, Western countries have evacuated nearly 100,000 people. But they acknowledge that thousands will be left behind when the last US troops leave at the end of the month.

Several Western countries said the mass airlift of civilians was coming to an end and announced their last remaining troops had left the country.

The American casualties in Thursday's attack were believed to be the most US troops killed in Afghanistan in a single incident since 30 personnel died when a helicopter was shot down in 2011.

The US deaths were the first in action in Afghanistan in 18 months, a fact likely to be cited by critics who accuse Biden of recklessly abandoning a stable and hard-won status quo by ordering an abrupt pullout.

© RAW 2021

Officials are still seeking to confirm whether any Australian citizens or visa holders were injured in the Kabul airport bombings.

And there are fears more bombings could occur.

"Australian condemns the evil, the calculated and inhuman attacks that were undertaken in Kabul overnight on the innocent and on the brave," Prime Minister Scott Morrison told reporters on Friday.

"We join with our American and Afghan friends in mourning their terrible and awful loss."

The blasts, attributed to terrorist organisation Islamic State Khorasan, killed more than 60 civilians and 13 US military personnel.

Over a period of nine frantic days, Australian forces were able to evacuate 4100 people out of Taliban-held Kabul, thanks to the presence of American and British defence forces guarding the airport.

The evacuees included around 3200 Australians and visa holders and 800 people from coalition partner countries.

There are currently 2500 people staying at Australia's Dubai air base and 783 have either come to Australia or other countries.

Foreign Minister Marise Payne warned of a high threat of further terror attacks, meaning Australian evacuation flights had ceased.

"We know that this is a very distressing situation for Australians still in Kabul, for people with visas and for families and friends who are here in Australia," Senator Payne said.

Mr Morrison said further opportunities to get remaining Afghan visa holders out would be "very restricted".

People were warned not to travel to Kabul airport but move to a safe location and register with the Department of Foreign Affairs and Trade if they had not already done so.

Lawyer Glenn Kolomeitz said about 1000 embassy guards, interpreters and their families who helped Australian forces remained in Afghanistan.

He served in Afghanistan and represents hundreds of Afghans entitled to protection in Australia.

As far as he knew, none of his clients were caught up in the bombings.

An interpreter family got through the airport gates just before the attacks.

Defence Minister Peter Dutton signalled Australia would offer assistance to any US mission to hunt down the people behind the attacks.

"Australia has worked alongside the United States in every major battle in modern history and we will continue to work with the American allies," he said.

"We've stood by them through thick and thin and we will continue to do that into the future."

Federal Labor held grave concerns for Australian citizens and visa holders still in Afghanistan who could no longer travel safely to Kabul airport.

"This was a despicable act against Afghans seeking security and those who were helping them," opposition leader Anthony Albanese said in a statement with foreign affairs spokeswoman Penny Wong and defence spokesman Brendan O'Connor.

"We grieve with the people of Afghanistan today. We grieve with our US allies - their work has saved many thousands of people."

© AAP 2021

Scott Morrison has condemned as evil and inhuman terrorist attacks in Afghanistan that killed more than 60 Afghans and 13 American troops in Kabul.

No Australian troops or officials died in the twin blasts which have been attributed to terrorist organisation Islamic State Khorasan.

But it is unclear whether Australian citizens, permanent residents or visa holders have been caught up in the bloodshed.

The prime minister said Australia joined with American and Afghan friends in mourning the terrible loss.

"Australian condemns the evil, the calculated and inhuman attacks that were undertaken in Kabul overnight on the innocent and on the brave," Mr Morrison told reporters on Friday.

Over a period of nine frantic days, Australian forces were able to evacuate 4100 people out of Taliban-held Kabul, thanks to the presence of American and British defence forces guarding the airport.

The evacuees included around 3200 Australians and visa holders and 800 people from coalition partner countries.

There are currently 2500 people staying at Australia's Dubai air base and 783 have either come to Australia or other countries.

Foreign Minister Marise Payne warned of a high threat of further terror attacks, meaning Australian evacuation flights had ceased.

"We know that this is a very distressing situation for Australians still in Kabul, for people with visas and for families and friends who are here in Australia," Senator Payne said.

Mr Morrison said further opportunities to get remaining Afghan visa holders out would be "very restricted".

People were warned not to travel to Kabul airport but move to a safe location and register with the Department of Foreign Affairs and Trade if they had not already done so.

Lawyer Glenn Kolomeitz said about 1000 embassy guards, interpreters and their families who helped Australian forces remained in Afghanistan.

Mr Kolomeitz served in Afghanistan and represents hundreds of Afghans entitled to protection in Australia.

As far as he knew, none of his clients were caught up in the bombings.

An interpreter family got through the airport gates just before the attacks.

US President Joe Biden has vowed to hunt down the people behind the attacks.

Defence Minister Peter Dutton signalled Australia would offer assistance if required.

"Australia has worked alongside the United States in every major battle in modern history and we will continue to work with the American allies," he said.

"We've stood by them through thick and thin and we will continue to do that into the future."

Labor's foreign affairs spokeswoman Penny Wong said there were grave concerns for Australian citizens and visa holders still in Afghanistan.

The Afghan Australian Advocacy Network's Arif Hussein said the irresponsible troop withdrawal directly contributed to the attacks and the current humanitarian crisis.

"After two decades of intervention and promises, the Afghan people are now abandoned to face the double threat of a Taliban rule, and ISKP attacks with the devastating consequence seen overnight," he said.

Australian Human Rights Commission president Rosalind Croucher urged the government to boost the humanitarian intake beyond the 3000 places set aside.

"We have asked for an urgent reassessment of all Afghan asylum seekers who have not received a positive protection finding, in light of the changed conditions," she said.

© AAP 2021