A file photo of the Iranian embassy in Vienna. Photo: file  

VIENNA: Heightened security measures have been ordered at embassies and other diplomatic buildings in Vienna after a soldier stationed outside the residence of the Iranian ambassador to Austria shot dead a man who tried to stab him, police said on Monday.

The 26-year-old assailant?s motive for the attack, which took place around 11:30 pm, was unclear and video footage would be reviewed, a police spokesman said.

?The attacker stabbed the soldier repeatedly. He was only saved by a stab-proof vest,? the spokesman said, adding that the two men ended up grappling on the ground.

?The soldier defended himself well and was then able to reach for his service weapon and fire shots,? he added.

The incident is reported four days after four people were seriously wounded in two knife attacks in a district Vienna, but a motive or any connection between the assaults was unclear, a police spokesman said.

The stabbings - the first of which occurred in Vienna?s Second District, which includes the famous Prater park as well as the Praterstern transport hub. 

?A man attacked a family - a father, a mother and their 17-year-old daughter - with a knife. The three people were seriously injured and their lives are in danger,? the spokesman said, adding later that they were Austrian citizens.

?And half an hour later, there was another attack ... at Praterstern and here a person was also seriously injured and their life is in danger. We do not know to what extent there is a connection here and any motive remains unclear,? he said.