POLICE searching a farm for a gunman who killed four people in central Austria say they have found the charred body of what they believe was the suspect.

Regional police spokesman Roland Scherscher says the body was discovered early Wednesday in a compartment behind a double wall of one of the buildings on the farm grounds.

The body was found more than a day after the gunman barricaded himself in a farm building near Melk, a town 70km west of Vienna.

Scherscher told reporters that forensic experts still had to identify the body but police believe it was that of the gunman, who apparently set himself ablaze.

After a 12-hour standoff in which tanks were called in, police stormed the building with body armor and assault weapons and were searching for the suspect, Interior Ministry spokesman Karl-Heinz Grundboeck said.

It wasn't immediately clear whether he was still in the building and the search was widening to other nearby buildings on the farm grounds.

The hunt stretched on more than three hours.

The gunman reportedly has large amounts of ammunition and a powerful hunting rifle able to pierce protective clothing. Mr Baumschlager called the situation "terrible and very explosive".

Reports said that "Cobra" police commandos had late on Monday attempted to stop the man, a well-known poacher thought to be in his mid-50s, in his car near Annaberg after a tip-off that he was hunting illegally.

He opened fire, however, reportedly after driving into a ditch, shooting one of the police commandos in the neck, who died two hours later in hospital.

While the commando was still receiving medical attention the poacher opened fire again, killing an ambulance driver and leaving a second policeman injured.

The suspect then fled on foot and opened fire on two other police officers, killing one and taking the other hostage, reports said.

He stole their police car and drove, with his prisoner, some 60 kilometres to his farmhouse.

Police said the dead body of the officer had been found in the police car at the farm.

The house has been surrounded since around 7am local time (3pm AEST yesterday) by some 100 police, who have so far failed to make contact with the gunman, despite help from acquaintances.

In the meantime he has fired several shots at the police. An AFP photographer at a nearby police roadblock saw three army tanks heading for the farmhouse.

Reports said that the man's children may be inside the house with him. The surrounding area has been cordoned off.

The poacher was well known in the local area for giving police and licensed hunters the run-around, often leaving the heads of dead animals on roads.

He was said to have had his hunting licence revoked several years ago.

Originally published as Cop-killer burns himself to death