Victoria has reported four new local COVID-19 cases as Premier Daniel Andrews defends the border bubble crackdown.

All of Tuesday’s locally acquired cases are linked to the state’s current outbreaks and were in isolation for their entire infectious period.

It is the third day in a row no new cases have spent any time in the community while infectious, with the number of exposure sites across the state falling to 56.

Tweet from @VicGovDH

Another returned traveller has also tested positive in hotel quarantine as active cases dropped to 124.

More than 22,000 test results were received in the 24 hours to Tuesday morning, while about 16,500 vaccine doses were administered at state-run sites.

It comes as Victoria bans non-essential movement across state lines because of the hovering threat of Sydney’s Delta variant outbreak.

From 11.59pm on Tuesday, border-bubble residents will only be able to state-hop for six reasons including medical care, compassionate purposes, work, education, playing sport or getting vaccinated.

The new measure applies to residents on both sides of the border, who must also not travel any further than necessary for that specific purpose.

Premier Daniel Andrews defended the call despite no cases being found in NSW border communities, alluding to counterpart Gladys Berejiklian’s refusal to set up a “ring of steel” around Sydney.

“We don’t have the settings in Sydney that we would like,” he said on Tuesday.

“But that isn’t a matter for us. So therefore we have to have a series of rules and series of changes that make that NSW-Victoria border as strong as it practically can be.”

Mr Andrews also shot down growing calls for the state to roll out rapid antigen testing, including for one-off events such as the AFL grand final.

Opposition Leader Michael O’Brien has been spruiking the technology, taking a 20-minute test on the front steps of state parliament on Tuesday morning.

He wants rapid testing to be used to screen visitors into aged-care homes and hospitals, as well as fans attending major events after recent exposures at the MCG and AAMI Park.

But Mr Andrews remains unconvinced the tests are reliable enough, including for a mooted plan to boost MCG crowd numbers up to 100,000 for the AFL grand final in late September.

“The advice says they wouldn’t work,” he said.

“You’re not going to see me ditching advice in favour of political stunts.”

-AAP