Iran's intelligence services say they 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.
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".
Tondar is thought to be the military arm of a little-known Los Angeles-based monarchist group called Kingdom Assembly of Iran.
Kingdom Assembly of Iran 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 electronics engineer born in 1955.
The website said he is Iranian-German and lived in Germany before moving to Los Angeles in 2003.
The Iranian ministry statement said Sharmahd planned and directed an explosion at a religious centre in the southern city of Shiraz in 2008 that killed 14 people and wounded 215.
It said Iranian intelligence aborted several other plots in more recent years, including the blowing up the shrine of Ayatollah Ruhollah Khomeini, the late founder of the Islamic Republic.
It did not say when the alleged plot was aborted.
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.
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.
Australian Associated Press