Citing experts, Victoria deputy premier James Merlino said it's possible aftershocks could continue for months.
"Geoscience have confirmed there is a possibility that we may receive further aftershocks and potential risk of further earthquakes," he said in a press conference. "Indeed, more aftershocks could occur for weeks, if not months."
Geoscience Australia said there was a magnitude 5.8 earthquake — that was 10km deep — occurred with an epicentre near Mansfield in Victoria.
Mansfield is a small town in the foothills of the Victorian Alps. It is about 180km northeast of Melbourne by road.
"Widespread felt reports. If you have building damage or require SES assistance, phone 132500 and please be patient as lines may be busy," it said. "There is no tsunami threat."
A second quake, understood to be an aftershock and registering a magnitude of 4.0, has taken place in the same location.
According to Geoscience Australia the first quake was at 9.15am local time, and the second at 9.33am.
A third quake, registering a magnitude of 3.1 at a depth of 6km, hit at 9.54am nearby.
Residents from as far away as Dubbo in NSW have reported tremors from the quake, as well as in Sydney, regional New South Wales, the ACT, Adelaide and Launceston in Tasmania.
Images from Chapel St in Melbourne show bricks strewn across the road and footpath from what looks to be a Betty's Burgers store — believed to be due to quake damage.
Merlino said building damage has been reported across Kensington, Ascot Vale, Prahran, Balwyn, Elsternwick, Northcote and West Melbourne.
Given the unrest on the streets of Melbourne in recent days, Deputy Police Commissioner Rick Nugent told 3AW he initially feared the shaking was the result of an explosion.
"We have that new Victoria Police building on Spencer Street, I'm on the 37th floor, so it's up rather high, but it really did move," he said.
"I just wondered … what now? After what we've endured in this great city."
The Prime Minister gave a press conference from Washington DC this morning, saying the earthquakes are a "very, very disturbing event" but there's some good news.
"At this stage, we have had no reports of serious injuries or worse and that is very good news and we hope that good news will continue but we will get further reports as the night unfolds here in the United States," he said.
"It can be a very, very disturbing event for an earthquake of this nature. They are very rare events in Australia and as a result, I am sure people would have been quite depressed and disturbed by that, particularly in the most immediate area affected.
"The agencies at a State Government level are there, responding and the Federal Government will provide the support that is necessary and will be in touch further with the Premier."
A seismologist has told ABC radio in Melbourne this morning that it was the biggest earthquake Victoria has experienced since European settlement and there will be aftershocks, potentially one magnitude lower.
Garry Gibson said the last time Victoria felt anything like this was in 2009 when there was a 5.5 magnitude earthquake. Australia-wide, we had a bigger one, a magnitude 6.1, or 6.2 near Broome in WA in 2019.
Mark Holcombe, the mayor of Mansfield, which was the epicentre of the quake, said it was "really strong" and caught everybody off-guard.
"It came right out of left field. We don't have earthquakes, that I am aware of, none of the locals I spoke to this morning had that experience with earthquakes here before, so it is one right out of left field. It was just a really big crumble," he told ABC Breakfast.
"It was really strong. I was sitting down at work at my desk and I needed to run outside, it took me awhile to work out what it was.
"I have been in earthquakes overseas before and it seemed to go on longer than I have experienced before. The other thing that surprised me was how noisy it was. It was a real rumbling like a truck going past."
The shudders were felt by the ABC Breakfast newsroom in Melbourne, where reporters said it was "quite frightening".
Host Michael Rowlands said: "It was quite frightening. I think you would agree.
"We were chatting here in the studio after the show, after we threw to you in the mornings coverage. We were chatting away and all of a sudden the studio started shaking, not to shaking and a minor violently.
