Victoria Police Commissioner Graham Ashton said security arrangements across the region as well as other public events, are being reassessed.
Extra police officers are likely to attend the events.
A Somalian man went on a knife rampage in central Melbourne today, stabbing three people after setting a car full of explosives on fire.
Police said they found his pick-up truck full of gas cylinders in what they are now treating as terrorism.
The knifeman then set fire to his vehicle before exiting to stab three people.
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One person has died.
Video footage showed the attacker lunging at police with a knife as they tried to contain him.
He was shot by an officer and was rushed to hospital, but he has since died.
One of his victims sustained significant head injuries.
Police could not confirm reports the attacker had shouted “Allahu Akbar” as he launched his attack.
Australia will join the world in remembering those who lost their lives in World War 1 and 2 on Remembrance Sunday this weekend.
This year is of particular significance as it marks 100 years since the end of World War 1.
Australia will commemorate Remembrance Day across the country with services at war memorials.
The biggest will be at the Australian War Memorial in Canberra, where dignitaries and diplomats will lay wreaths.
Australia’s Federation Guard and the Band of the Royal Military College, Duntroon will be on parade.
In Melbourne crowds will gather at the Shrine of Remembrance on St Kilda Road for a minute’s silence at 11am.
During World War 1 300,000 Australians fought with the allied forces. Of those 60,000 died and 156,000 taken prisoner.
The Melbourne attacker and some of his family members were known to counter-terrorism police.
Mr Ashton told a press conference: “We are treating this as a terrorism incident.
“He is known to both Victoria Police and federal intelligence authorities. There is no ongoing threat that we are aware of in relation to that individual.
“Having said that this is an ongoing investigation.”
Police said the man had punched a police officer in the face through his car window when he first arrived at the scene.
Officers tried to use pepper spray and a Taser to stop the attacker.
Other people on the scene threw chairs and tried to ram a shopping trolley into the attacker to take him out.
Victoria’s Premier Daniel Andrews praised members of the public for stepping in.
He said: “Stranger and bystanders, who knew nobody involved, stepped in without a moment’s hesitation…they too are people whose qualities make us all proud as well.
“We extend our thoughts and prayers to all who are injured and extend our deepest, deepest sympathies.”
He urged witnesses and others affected to contact Lifeline, Gridline and Beyond Blue.
He added: “These are traumatic events, they are terrifying.
“Many will have seen them first hand.”
Two victims are still in hospital with non-life-threatening injuries.
All victims are men, according to Mr Ashton.