9News understands Premier Daniel Andrews will announce the 650 cases and more than a dozen deaths at a media briefing scheduled for about 1pm.
The Premier said new business and industry restrictions will be announced tomorrow.
The new Stage Four measures will be in force from 6pm tonight and run until September 13.
Students of parents who need to keep working will be allowed to go to school and be supervised, but only if it is absolutely necessary, the premier said.
Andrews said his government was deeply anxious that 49 "mystery cases" identified on Saturday could indicate the virus was spreading widely through the Melbourne community and confirmed he was in discussions with Australian Prime Minister Scott Morrison about tougher restrictions. "We have to clamp down on this, and get to the point where we have much lower numbers as quickly as we possibly can", Andrews said.
Among those to breach coronavirus restrictions were a group of five people found attending a birthday celebration at a licensed venue in Melbourne's CBD.
Mr Andrews has declared the six weeks a "state of disaster" in addition to the state's ongoing "state of emergency". "This means that police and others have additional powers". We've got to limit the amount of movement, therefore limiting the amount of transmission of this virus.
"What I would say is this is not about human rights, it's about human life and all of us need to make sure we play our part in making sure we don't have more families planning funerals", he said.
Melbourne is facing tougher lockdown restrictions within days, which could mean more businesses in Australia's second-largest city closing their doors, stricter stay-at-home rules and drastically cut public transport services.
Only one person from each household will be permitted to go shopping and they will not be able to travel further than 5km from their home.
Metropolitan Melbourne will be under a nightly curfew, between the hours of 8pm to 5am, from Sunday night with some exemptions for those providing care and travelling to and from work.
Regional Victoria will enter Stage Three restrictions, with the Premier saying the order is to stay home "except for the four reasons for leaving".
Thirty-seven of the new cases are linked to known outbreaks while 360 remain under investigation.
Active cases in the state's aged care system on Saturday surged beyond 1000 - with outbreaks in 100 different homes - for the first time since the pandemic began.
Cases of coronavirus in Victoria have reportedly climbed to another astounding high with more than 600 new infections recorded across the state.