A group of 10 officers had attended a property on Rayner Track in Porepunkah, about 300km northeast of Melbourne, at 10.30am on Tuesday to execute a search warrant.
Two officers were killed when a man shot at them. A third was seriously injured and is undergoing surgery.
A "significant" search is underway to find the man, who police sources said was believed to be travelling with his wife and children.
"We have deployed all specialist resources into the area to arrest the person responsible," Police Commissioner Mike Bush said.
"This is a terribly tragic event for the police family, not just here but across the country.
"We all feel this."
The officers were ambushed by the alleged perpetrator who is believed to be a sovereign citizen, police sources not authorised to comment on the situation told AAP.
Hundreds of officers have been deployed to the town and its surrounds as a police helicopter circles overhead.
Police are urging the town's 1000 residents to remain indoors and those in nearby areas to stay away.
Local post office and fuel station worker Reddy Gopi said the distressing attack took place about one kilometre from his workplace.
"Everyone is in a bit of a panic," Mr Gopi told AAP.
"There were 200 to 300 policemen searching here and we've got a helicopter in the Porepunkah and Bright areas searching everywhere, and they've closed pretty much all the roads."
Mr Gopi said he saw five SWAT teams speed by while police cars continue to scan the empty streets for the perpetrator.
"It's pretty silent. It's like a ghost town," he said.
Prime Minister Anthony Albanese said his government's thoughts were with the force.
"The men and women who wear our uniform and wear the uniform of the police force, take risks each and every day," he told reporters in Canberra.
The Police Association Victoria Secretary Wayne Gatt said the "senseless murder" of their mates has left every officer mourning.
"They will go home and hug their families tighter than usual, in the sad and sobering knowledge that two of their colleagues lost that privilege in service of the community," he said.
Following the incident, Porepunkah Primary School, Bright P-12 College and early childhood services in the area went into lockdown.
Parents at both schools have been allowed to collect their children at the end of the school day.
All council buildings in the Alpine Shire Council have been closed until further notice, as has Porepunkah Airfield.
Mayor Sarah Nicholas said it was a day of deep sorrow and shock for our community and offered her thoughts and support for the loved ones of the officers killed.
The airfield's reporting officer Mark Simpson said the SES and police were setting up tents and using the airfield to re-fuel their helicopters as they continued their search.
"It's quite traumatic. Police officers go to work, they've got to do their job, and they expect to go home," he told AAP.
Officers across the nation were shocked and saddened by the "callous murder of two Victorian police officers and the serious wounding of another", Police Federation of Australia president Kevin Morton said.
Australian Federal Police Association president Alex Caruana said the group's members stood in solidarity with their Victorian counterparts.
Premier Jacinta Allan has praised officers for their extraordinary bravery and courage while opposition leader Brad Battin said police officers went to work each day knowing there was risk.
The deaths mark the state's biggest loss of police life since the 2020 Eastern Freeway crash when four officers died after a truck veered into the emergency lane and hit them as they were impounding a vehicle.
Two Queensland officers and a neighbour were shot dead by so-called sovereign citizens in an ambush in the town of Wieambilla in 2022 after they were called to a welfare check.
Tasmanian officer was Keith Smith was shot dead in June as he approached a home in the state's northwest to deliver a court-ordered home repossession warrant.
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