Austrian police have found the charred remains of a man suspected of shooting dead four people, including three policemen, in the basement of a farmhouse he had holed up in.

The body of the suspect, named as Alois Huber, 55, was found in a secret room behind a false wall in a cellar by security forces who stormed the building near Melk, a village in the province of Lower Austria, at the end of a 12-hour standoff.

Authorities believe Huber, a notorious deer poacher, set himself ablaze.

"The room could only be entered through a door hidden in a wall," regional police spokesman Roland Scherscher said. "One had to push against the wall to enter the room. The police forced open the door and wanted to enter the room. But it had been set ablaze."

SWAT teams discovered a body after extinguishing the fire. Scherscher said the corpse was so badly burned that it could not be identified, but police assumed it was that of the gunman.

Huber, the owner of a trucking firm, allegedly went on a killing spree after being stopped by police for illegal night-time hunting on a road near an area of wilderness, west of Vienna.

He fled by car but crashed into a ditch near the central Austrian town of Annaberg.

As police approached he opened fire, injuring a police officer, who later died in hospital, and killing a paramedic who went to the officer's rescue.

A second policeman was also shot and injured but is expected to recover.

Huber escaped on foot before eventually bumping into two policemen at a roadblock. He shot one dead and hijacked their police car, taking the second hostage.

He drove to the farmhouse and barricaded himself in. The body of the policeman taken hostage was found shot dead in the patrol car abandoned near the farm by heavily armed security forces, who surrounded the area.

A tense standoff ensued. Huber shot sporadically at Swat teams that cordoned off the area, backed by armoured vehicles and three Austrian army tanks.

Scherscher said he could not confirm reports that the gunman had been shot in the abdomen by police before seeking refuge inside the farm.

The provincial government of Lower Austria ordered black flags flown from all public buildings.

Alois Huber Austria gunman
Alois Huber, 55, has been named as the suspect gunman who killed four people in Austria (Twitter)