The motive for the attack is not yet known.
Police say an Austrian soldier shot dead a knife-wielding man who attacked him outside the Iranian ambassador's residence in Vienna.
Police said the guard, a 23-year-old Austrian soldier, first tried to deter the assailant in Sunday night's incident with pepper spray.
"The assailant is about 26 years old and apparently possesses Austrian nationality, and there's no information on his identity and motivation for the act", Foreign Ministry spokesman Bahram Qassemi said on Monday.
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The soldier, who was standing guard outside the building, suffered a wound to his upper arm in the attack.
The soldier has cuts on his right hand, but the protective vest has prevented more serious injuries.
Police have ordered reinforcements around all diplomatic missions in the Austrian capital, which is also home to many worldwide organisations. As a result of the incident, security has been increased at all diplomatic institutions across Vienna, according to the APA news agency.
In the Austrian capital last week, four people were injured in knife attacks, DPA recalls.