Two police officers dead, gunman at large in rural town

Two officers were killed at a rural property on Tuesday in an ambush attack involving a perpetrator believed to be a sovereign citizen, police sources not authorised to comment on the situation told AAP.

Victoria Police are yet to confirm any details.

Police are urging the public to stay clear of the dangerous and active situation in the town, known for its sweeping vineyards and scenery.

Prime Minister Anthony Albanese said the government's thoughts were with the force, acknowledging there were concerns for "some of the police officers who are involved".

"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.

Australian Federal Police Commissioner Reece Kershaw offered his thoughts and prayers to the officers involved.

"We hope that they are all safe and well," he said. 

"However, we're hearing that there are some grave concerns for some of those police officers, and our hearts go out to the community."

The Police Association Victoria told AAP it was aware of a critical incident that is impacting members.

"We have sent critical incident support teams to the area to assist and support the impacted members, their families and colleagues," the association said. 

Following the incident, Porepunkah Primary School went into lockdown.

Principal Jill Gillies said the school practised drills all the time, so the children were able to face the lockdown in a calm manner and were being entertained in their classrooms.

"We went into pre-emptive lockdown around 1130am. We were told that there was a situation unfolding," she told ABC radio.

"Just for the safety of the kids and just to keep everything nice and calm, we went into lockdown."

The school has 104 children enrolled, and is located in the centre of the small town.

Premier Jacinta Allan has been briefed by Victoria Police chief commissioner Mike Bush on the ongoing active situation, urging people to avoid the area.

"Victoria Police officers, and all our first responders, show extraordinary bravery and courage every single day," she said on social media.

"They are the best of us – and the thoughts of all Victorians are with them today."

Police officers woke up and went to work each day knowing there was risk, state opposition leader Brad Battin said.

"Events like this will impact each and every police officer across Victoria and across Australia," the former officer said.

People have been told to avoid the area, which is home to about 1000 residents and supports a number of vineyards.

Locals told AAP they saw a number of police cars heading into the town.

"This is still an active incident and we will provide more information when it's operationally safe to do so," Victoria Police said.