Premier Daniel Andrews on Monday announced the extension, as well as a raft of tougher restrictions, after the state recorded 22 new local COVID-19 cases, including five mystery cases.

A 9pm to 5am curfew, which was in place during the state's second wave last year, will return from 11.59pm on Monday, while permits for work will be reintroduced and playgrounds closed.

Chief Health Officer Brett Sutton said the suite of measures was needed to ensure COVID-19 cases did not spiral out of control.

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"A grumbling few cases now is the hundreds in a fortnight or the thousands in a month," he told reporters.

Mr Andrews said the state had no choice given the number of mystery cases, illegal gatherings at the weekend and the number of children spreading the virus.

"We've seen lots of different people flouting these rules, not doing as they should, making really poor choices," he said.

In particular, Mr Andrews said an engagement party last week of 69 people was particularly egregious.

"There has been transmission at that event," he said.

"But what makes me really angry about that event is that each of those 69 people will have to be interviewed. Their close contact also have to be spoken to, tested."

A mother and son from St Kilda East, the heart of the city's Jewish community, tested positive for COVID-19 at the weekend, despite having no known links to other cases.

It is believed one of them attended an engagement party, allegedly held in breach of lockdown restrictions earlier in the week.

"They are s***ty choices," Mr Andrews said, adding the family was not a victim following intense backlash.

"The is not an act of faith, this is not part of any cultural practice. This is just bad behaviour."

AAP understands at least two medical professionals attended the event, while another guest works as a prison chaplain, though they haven't conducted a visit since February.

The newly elected president of the Jewish Community Council of Victoria, Daniel Aghion, called for calm and said anyone concerned about exposure should contact authorities, while the Rabbinical Council of Victoria urged the community to follow restrictions.

Chief Commissioner Shane Patton said police were investigating the party and expects to fine every adult attendee.

"If you take off a few for each child, that's going to be over $350,000 worth of fines. That's an expensive engagement party," he said.

In a video, seen by AAP, dozens of people, who aren't wearing masks, are gathered in what appears to be a private residence, listening to a man give a speech.

"Clearly this is legal as a group therapy session. That's why my father's here," the man jokes.

Another party member adds: "He's a mental health clinician."

Seventeen of Monday's new cases are linked to known outbreaks, while 14 cases were in quarantine throughout their entire infectious period.

Some 29,986 tests were processed in the 24 hours to Monday morning, while 19,880 Victorian received a vaccine dose at a state-run hub.

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