Police have found a gun near Rod Laver Arena and established a crime scene as they search for a gunman in Melbourne's MCG and Olympic Park area following a high-speed chase in the city's east this morning.

Police have named the suspected gunman as 19-year-old David Paul Rowntree who they say is known to them and may be dangerous.

The area around the stadiums is no longer cordoned off, but police are urging people who do not have urgent business in the precinct to stay away.

Special Operations Group officers are patrolling the site but roads have been reopened and train and tram services are getting back to normal after being shut down earlier today.

Earlier, police described the gunman as being aged in his 20s with straight, dark hair and said he was wearing a dark jacket with a red or orange T-shirt and silver trackpants.

They say he is connected to two vehicles stolen in Melbourne's east, one of which was used in an armed robbery at Bulleen.

Police believe the man has abandoned his vehicle and is now on foot, but they say no shots have been fired.

They warn the suspect should not be approached under any circumstances.

Sergeant Adrian Kelty from the Victoria Police Media Unit says the man was seen by witnesses, armed with a shotgun.

"At this stage, we've got the police helicopter and we've got members on foot and in vehicles, still patrolling the east Melbourne area," he said.

"We did find a stolen vehicle which was stolen from the Bulleen area earlier this morning. That's the vehicle we pursued from the area earlier on [and] we found that in the car park of Rod Laver Arena.

"The last sighting of the offender was actually going across the Rod Laver Bridge towards the MCG... at 10.30am."

Superintendent Rod Wilson says the man is known to police and may be dangerous.

"Our units have a good idea who they're looking for so we'll obviously keep up that level of commitment in this area throughout the day," he said.

"Over the next few hours there will be a highly visual police presence, so all I'm saying to people [is] obviously be very careful, if you don't have to go out, stay indoors, and if you've got any suspicious behaviour to report, there's going to be a lot of police patrolling.

"We've isolated the area and we'll continue to search for the suspect."

The Armed Crime Taskforce has now taken over the investigation.

High-speed chase

The search follows a high-speed chase along the Monash Freeway this morning, during which two police cars were rammed by a car with stolen number plates.

Police started following the car in Cookson Street, Camberwell, about 9:30am AEST, but lost sight of it as it sped onto the Monash Freeway, then Citylink and through the Domain tunnel.

A police officer who was in the car that was rammed on the Monash Freeway has been taken to the Box Hill hospital with back injuries.

A witness, John, says the police cars were badly damaged.

"Just after the Toorak Road turn-off there are two unmarked police cars parked on the right hand side inbound on the Monash," he said.

"They both seem to have damage from being rammed, and they are being put onto tow vehicles to be towed away."