Moscow has demanded the release of a Russian space agency official who was arrested in Salzburg, Austria, this week on suspicion of spying.
Russian President Vladimir Putin (R) visited Austria just before the arrest
The Russian was suspected of receiving sensitive information from an Austrian military officer, who was also arrested, Austrian officials said.
Russia said he had diplomatic immunity because he was attending a UN meeting in Vienna at the time of his arrest.
Austria's foreign ministry says it is trying to confirm the immunity claim.
The man was a member of the Russian delegation to the 50th session of the UN's Committee on the Peaceful Uses of Outer Space, Russia's space agency said.
Russia summoned Austria's Moscow ambassador, Martin Vukovic, to demand the release of the unnamed space agency official.
The man was arrested on Monday at the main train station in Salzburg.
The Austrian military officer was also arrested on Monday in the town of Gmunden, east of Salzburg.
"This act by Austria is seen as being unfriendly and harming bilateral relations," Russia's foreign ministry said.
"The incident does not strengthen Austria's position as a location for the headquarters of a number of international organisations in the UN system."
Gerald Jarosch, from the office of Austria's state prosecutor, said the Russian official would be investigated for espionage in Vienna, a process that could take months.
The official also faces deportation to Germany, which has a warrant for his arrest as well, Mr Jarosch said.
Russian President Vladimir Putin visited Austria three weeks before the arrest.