Two bomb disposal experts were killed when an American Second World War bomb they were attempting to defuse in Salzburg's main rail station blew up.
A third expert from the Austrian interior ministry was critically injured in the blast.
The 550 pound bomb exploded as they were attempting to remove the chemical detonator, blasting a crater 20 feet deep and causing serious damage to surrounding vehicles and buildings.
Up to 300 people living near the site of the operation had been evacuated beforehand.
A bomb disposal expert from Germany had earlier warned of the dangers involved in defusing such bombs.
"This type of bomb is especially dangerous because it is equipped with a chemical fuse," said Joachim Wittig.
He added that ground water entering the pit around the bomb made the operation especially dangerous.
Salzburg's railway lines were a major target for allied bombers during the war, and many bombs from that period remain in the area.
AP