An Iranian diplomat was taken into custody in Belgium on Wednesday on suspicion of involvement in an alleged plot to bomb an Iranian opposition rally in France.
An investigating magistrate earlier questioned the Iranian, normally based in Vienna, in the northern Belgian city of Antwerp, the Federal Prosecutor's Office said in a statement.
Prosecutors said Tuesday that the suspect, previously identified as Assadollah Assadi, had been extradited to Belgium from Germany.
Tehran summoned the German ambassador on Wednesday to protest the extradition, which the foreign ministry said was "caused by a fabricated conspiracy by enemies of Iran and European relations".
Iran has denied French accusations that Assadi was involved in a plot targeting an annual gathering of the National Council of Resistance of Iran (NCRI) on June 30 just outside Paris.
Belgian anti-terrorism prosecutors announced on July 2 that they had foiled the plot. They then requested the extradition of both Assadi and a man identified as Merhad A., who was detained in Paris.
Belgian police believe Merhad A. is an accomplice of a husband and wife team caught in Brussels in possession of 500 grammes (about a pound) of the powerful explosive TATP and a detonator.
All three are Belgian nationals of Iranian origin.
The accusations come at a particularly sensitive time as Iran works with European powers to salvage the 2015 nuclear deal, abandoned by the United States earlier this year.