The harsher rules come after multiple rules breaches, including an illegal engagement party and pub crawls, and 22 cases confirmed on Monday.

Lockdown will be extended until September 2, with a 9pm to 5am curfew, which was in place during the state's second wave, returning from 11.59pm Monday.

Authorised workers will have to carry permits, playgrounds and public recreation equipment will close, exercise will be limited to two people and large-scale construction will be restricted to 25 per cent of staff.

There will be an increased police presence across Melbourne to ensure the rules are enforced.

Premier Daniel Andrews said the state had "no choice" but to toughen restrictions, given increasing mystery infections, the number of children infected and several illegal gatherings held at the weekend.

"I know people are weary. I know people are sick and tired of this," he told reporters.

"But each of us has to find it in ourselves to make good choices for these next couple of weeks to drive down these case numbers and to be in a position so that we can reopen."

Mr Andrews said he was particularly "angry and disappointed" to hear of an engagement party held last week by a prominent Jewish family in Melbourne's southeast.

Three people, including a mother and son in St Kilda East, have tested positive for COVID-19 following the event.

"They are s***ty choices and they will keep us all locked down for longer than we should be," Mr Andrews said, noting the vast majority of the Jewish community have been following restrictions.

"This 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 works as a prison chaplain, although they haven't conducted a visit since February.

Chief Commissioner Shane Patton said police expected to fine every adult attendee.

"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 unmasked people 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."

Some 69 people who attended the engagement are now self-isolating, as are 90 of their close contacts.

The Rabbinical Council of Victoria has urged the community to follow restrictions.

Chief Health Officer Brett Sutton said a "grumbling" number of daily cases could end up being 100 in a fortnight, or thousands in a month.

"We are right on the cliff edge here," he said.

"We are maybe just keeping up with this outbreak but we are not ahead of it in the way we need to be in order to achieve control."

State Opposition Leader Michael O'Brien said the curfew is an overreach from the government and described shutting down playgrounds as cruel.

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

There are currently more than 14,200 close contacts across Victoria and more than 500 exposure sites.

Six people are in hospital battling the virus, including a child in ICU in a stable condition.

Australian Associated Press