Victoria will enter a seven-day lockdown in an effort to contain a growing outbreak of the COVID-19 Delta variant in Melbourne's western suburbs.
Premier Daniel Andrews confirmed the lockdown will begin at 8pm on Thursday, after the state recorded eight new COVID-19 cases.
The same rules that applied during last month's lockdown will be reimposed, including the five-kilometre travel limit for exercise and shopping and compulsory masks indoors and outdoors.
"The advice to me from the experts if we were to wait even just a few days, is there is every chance that instead of being locked down for a week, this gets away from us and we are potentially locked down until we all get vaccinated," Mr Andrews said.
Victorians have been given less than four hours notice of the lockdown, unlike previous ones that started at midnight, because a previous outbreak was linked to a dinner on lockdown-eve, Mr Andrews said.
He said the national strategy for dealing with the Delta variant was to go hard and fast with lockdowns.
"You almost can't act fast enough," Mr Andrews said.
The sixth lockdown was prompted in part by fears a teacher at Al-Taqwa College in Truganina infected with COVID-19 may have unknowingly spread the virus while infectious.
She also passed the virus on to her partner and his parents.
It is unknown how the couple, who live in the Hobsons Bay area and are both in their 20s, caught the virus.
The Al-Taqwa College has now become a testing site and is offering vaccinations to staff and students.
Authorities are also racing to trace the source of their infection and that of a man in his 20s who lives in the Maribyrnong council.
He works at a warehouse in Derrimut and he and his housemate are now isolating.
The three other cases from Thursday's numbers are linked to the Moonee Valley testing site cluster.
It is the sixth lockdown for Victoria since the start of the pandemic and the fourth in 2021.
The state's fifth lockdown ended just nine days ago.
Mr Andrews said even though all the cases announced on Thursday are in Melbourne, sewage tests had detected virus fragments in the Wangaratta region.
Details of business support will be revealed on Friday.
Businesses that have already applied for support during the last lockdown are expected to receive payments again this time around, without having to file new paperwork.
Victoria has also requested extra Pfizer vaccines, following more doses being sent to NSW, which is in an extended lockdown battling its worst outbreak since the pandemic began.
For exposure sites visit www.coronavirus.vic.gov.au/exposure-sites
© AAP 2021