Iran said on Saturday its intelligence services have detained a US-based leader of a pro-monarchist group whom it accused of being behind a deadly 2008 bombing and of plotting other attacks, and that he is being held in Iran.
An intelligence ministry statement cited by state television did not say how, where or when the detention took place.
"Jamshid Sharmahd, the ringleader of the terrorist Tondar (Thunder) group, who directed armed and terrorist acts in Iran from America, was arrested following a complicated operation, and is now in (our agents') powerful hands," it said.
Television showed a video of a man identifying himself as Sharmahd and giving his date of birth. The man was later shown with a blindfold, saying: "They needed explosives and we provided it."
Tondar did not confirm the detention. In reaction to what it said were reports of Sharmahd's "abduction", the group said on its website it did not confirm "stories being told by various networks".
However it said in an earlier posting on social media that "Tondar ... will continue to fight even in the absence of a commander".
A US State Department spokeswoman said on Saturday that the US government was "aware of reports related to the detention of Mr. Sharmahd. The Iranian regime has a long history of detaining Iranians and foreign nationals on spurious charges. We urge Iran to be fully transparent and abide by all international legal standards."
Based in Los Angeles, the little-known Kingdom Assembly of Iran, or Tondar, says it seeks to restore the Iranian monarchy that was overthrown by the 1979 Islamic revolution. It runs pro-Iranian opposition radio and television stations abroad.
According to the group's website, Sharmahd is an Iranian-German electronics engineer who was born in 1955 and lived in Germany before moving to Los Angeles in 2003.
No comment was immediately available from the German foreign ministry.
The Iranian ministry statement said Sharmahd planned and directed an explosion at a religious center in the southern city of Shiraz in 2008 that killed 14 people and wounded 215.
It said Iranian intelligence had prevented several other plots in more recent years, including one, at an unspecified date, to blow up the shrine of Ayatollah Ruhollah Khomeini, the late founder of the Islamic Republic.
Intelligence Minister Mahmoud Alavi called Tondar the "most violence-prone" royalist opposition group.
"Despite our complaint to Interpol, Sharmahd would travel everywhere under his own name. This shows how empty anti-terror slogans by Americans and their Europeans allies are," he told state TV.
In 2019, Iran detained Ruhollah Zam, a Paris-based journalist turned activist, after apparently luring him to neighbouring Iraq, according to Iranian media reports at the time. Zam was sentenced to death on security charges in June.
Sharmahd's detention came at a time of particularly tense relations between longtime foes Washington and Tehran.
Iran's Foreign Minister Mohammad Javad Zarif urged the West in a Twitter post to "cease financing and harboring terrorists" who from "safe havens in US and Europe ... promote hatred, agitate & organize murder & mayhem, and shamelessly claim responsibility for the murder of innocent Iranian civilians".
The Iranian foreign ministry earlier said in a statement that Washington should be held accountable for backing "this terrorist group and other groups and criminals responsible for sabotage, armed and terrorist operations" from within the United States.
Tondar has claimed responsibility for some attacks, saying on its website it was behind the bombing of a seminary used by Revolutionary Guards in Shiraz in June 2019, and an explosion in a refinery in 2016.
In 2009, Iran executed three men convicted of involvement in the 2008 bombing.