Tehran: Iran called on the United States on Tuesday to extradite members of a "terrorist group" which the Islamic Republic has linked to this month`s killing of a university scientist in Tehran.
Iranian officials have blamed both Israel and the United States for the January 12 bomb attack that killed professor Massoud Ali-Mohammadi. Washington has dismissed the charge of US involvement as absurd.
Some Iranian media have also reported that a Western-based pro-monarchy group claimed responsibility for the attack, but have not said how they knew this.
On Tuesday, Foreign Ministry spokesman Ramin Mehmanparast named the group as Tondar (Thunder), without giving details. He said the Swiss Ambassador, who represents US interests in Iran, had been summoned to the Foreign Ministry on Monday.
"Regarding the assassination which was claimed by Tondar, we asked the Swiss embassy for an explanation on how the US accepted to have this terrorist group in their country," he told a weekly press briefing.
"They should be answerable about this and we want the criminals to be extradited to Iran," Mehmanparast said, without naming whom Tehran was seeking.
The United States cut relations with Tehran shortly after Iran`s 1979 Islamic revolution, which toppled the US-backed Shah.
Iranian officials have described the slain professor as a nuclear scientist but a spokesman said he did not work for the Atomic Energy Organisation at the centre of the Islamic Republic`s nuclear energy programme.
The West fears the programme is aimed at acquiring nuclear weapons but Tehran says it is only for generating electricity.
An opposition website has said Ali-Mohammadi was an opposition supporter who backed moderate candidate Mirhossein Mousavi in last June`s disputed election.
The January 12 bombing -- a rare attack in the Iranian capital -- occurred at a time of heightened tension in the country, seven months after a disputed Presidential Election plunged the major oil producer into turmoil.