Police searching a farm for a gunman who killed four people in central Austria said that they have found the charred body of what they believed was the suspect.

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

After a 12-hour standoff, police stormed the building with body armour and assault weapons. The body was found more than a day after the gunman barricaded himself in a farm building near Melk, a town 40 miles 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 on fire.

The killings began about 24 hours earlier, when police stopped the man on a road near a wilderness area west of Vienna where there has been frequent poaching. Austrian media said the man was a suspected poacher. Police named the suspect as 55-year-old Alois Huber.

Interior ministry spokesman Karl-Heinz Grundboeck said the gunman fled in his car, which landed in a ditch in the nearby town of Annaberg, then shot and wounded a member of Austria's Cobra Swat team at a police checkpoint. The police officer later died. An ambulance arrived, but the gunman shot and killed its driver as he tried to give first aid to the wounded policeman. The gunman also shot and wounded another officer at the scene.

Later on Tuesday, another officer who had been missing was found shot dead in his patrol car, said Grundboeck. Scherscher said that officer was apparently killed after the suspect carjacked the police vehicle and took him hostage.

The attacker then fatally shot another police officer at a roadblock before barricading himself in the farm building.

The provincial government of Lower Austria ordered black flags flown from all public buildings in honour of the gunman's victims.