They had allegedly planned to bomb the rally by an exiled Iranian opposition group in Villepinte near Paris that was attended by several US politicians.
German prosecutors said today that a court had two days earlier remanded Assadi in custody on charges of foreign intelligence activities and conspiracy to murder. They added that these charges did "not preclude" Assadi's extradition requested by Belgium.
Assadi was believed to be a member of Iran's Ministry of Intelligence and Security, which is tasked with the "observation and fight against opposition groups inside and outside Iran", the prosecutors' statement said.
The couple were arrested in Brussels on the day of the rally by Belgian security services who said they found them in possession of 500 grams (about one pound) of the volatile explosive TATP and a detonator.
They were identified only as Amir S., 38, and Nasimeh N., 33, and as being Belgian nationals of Iranian origin.
French police arrested another three people but later released two of them, French legal sources said.
Washington considers Iran to be the world's biggest state sponsor of terrorism because of its links with the Hezbollah militia in Lebanon, Hamas in the Palestinian territories and other networks in Iraq and Yemen.
The Paris rally by the National Council of Resistance of Iran was attended by Trump's personal lawyer, former New York mayor Rudy Giuliani, and former House speaker Newt Gingrich, who both urged "regime change" in Iran.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)