Melbourne's ever-growing mystery coronavirus case numbers are starting to centre around key suburbs, but not enough people are getting tested to work out how it is spreading.
Victoria recorded 24 new locally acquired coronavirus cases on the first day of stricter lockdown measures in Melbourne.
Of those, 21 are linked to known outbreaks, while the source of the remaining three are a mystery.
Fourteen of the 24 were in quarantine during their infectious period.
There were 31,519 tests processed on Monday.
"That is not high enough and I would ask every single Victorian, regardless of where you live, your circumstances, if you register any symptoms at all, please come forward and get tested," Victorian Premier Daniel Andrews told reporters on Tuesday.
Health department deputy secretary Kate Matson said the mystery cases were starting to centre in Melbourne's southeast - the local government areas of Glen Eira and Port Phillip.
"If you look at the exposure site map on our website, you can see 50-odd exposure sites running from South Melbourne, down the bay, down to Brighton," Ms Matson said.
"These cases aren't linked by age. They're not linked by faith. They aren't all in the same book club. They are not all on the same footy club.
"There is nothing linking these cases other than geography, which is why we do ask that testing rates increase in that area."
Some 31,519 tests were processed in the 24 hours to Tuesday morning, while 25,742 Victorians received a vaccine dose at a state-run hub.
Of Tuesday's 24 cases, three were from an illegal engagement party held last week in Caulfield North, in the City of Glen Eira, taking the total number of infections from the event to six.
It comes as the state government extended Melbourne's lockdown by two weeks, reintroduced a curfew between 9pm and 5am and closed playgrounds in an effort to contain the city's latest outbreak of the Delta coronavirus variant.
Exercise has also been limited to two people, large-scale construction restricted to 25 per cent of staff and people will not be allowed to remove their masks to drink alcohol in public.
From 11:59pm on Tuesday, authorised workers will be required to carry permits.
Overnight, the ACT was declared an extreme risk zone under Victoria's travel permit system, after its COVID-19 outbreak grew to 28 cases.
Anyone who has been in the ACT in the past 14 days cannot enter Victoria without an exemption or valid permit.
Greater Darwin and Katherine, which entered a 72-hour lockdown on Monday, were also reclassified as red zones, meaning anyone arriving in Victoria from the local government areas will need a permit and must quarantine for 14 days.
