Two Iranian university professors were targeted by assassins in separate but identical bomb attacks in Tehran on Monday, killing at least one of them, according to local press reports.
An Iranian state TV's website said one victim, a nuclear scientist, was killed, while there were conflicting reports of the fate of the second man.
The Fars television service said bombs were attached to both victims' cars by assassins on motorcycles. No further details were given on the identities of the attackers.
Fars accused agents of the United States and Israel of being behind the killings.
State broadcaster ISNA further named the two victims as Majid Shahriari and Fereydoun Abbasi, both professors at Tehran's Shahid Beheshti university.
Shahriari was killed, while Abbasi and his wife were injured and hospitalized, ISNA said.
In January, another Iranian nuclear scientist, Professor Massoud Ali-Mohammadi was also killed.
State media said at the time that Ali-Mohammadi was killed by a remote controlled bomb strapped to a motorcycle.
Then too, Iran accused Israel and the West of the attack on a "committed and revolutionary" scientist.
But an opposition website, Jaras, said Ali Mohhamadi was an opposition supporter who backed moderate candidate Mirhossein Mousavi in a disputed election, which plunged Iran into turmoil in mid-2009.
In February 2009, the Daily Telegraph, a British, newspaper, reported that Israel was assassinating Iranian nuclear scientists as part of a covert war against the Islamic Republic's illicit weapons program.
The Telegraph quoted Western intelligence analysts as saying that Israel's Mossad spy agency was behind the death of Ardeshire Hassanpour, a top nuclear scientist at Iran's Isfahan uranium plant who died mysteriously from"gas poisoning" in 2007.
Israel and the West accuse Iran of developing nuclear weapons, a charge the Iranians deny.