TEHERAN, Iran - Two assailants on a motorcycle attached magnetic bombs on Wednesday to the car of an Iranian university professor working at a key nuclear facility, killing him and wounding two others, Iran's Fars News Agencey reported.

The attack in Teheran strongly resembles earlier killings of scientists working on the country's controversial nuclear program.

The bomb explosion killed Mostafa Ahmadi Roshan, a chemistry expert and a director of the Natanz uranium enrichment facility in central Iran, the Fars News Agency reported.

The killing of Roshan was similar to previous assassinations of Iranian nuclear scientists that Teheran has blamed on Israel and the United States. Both countries have denied the accusations.

Israel blamed

Iran's First Vice-President Mohammad-Reza Rahimi said Israeli agents were the perpetrators of Wednesday's assassination of the Iranian nuclear staff, the official IRNA News Agency reported.

The enemies should know that they will not be able to stop Iran's scientific progress with terrorist acts, Rahimi was quoted as saying.

Iranian media reported earlier that Ahmadi Roshan, an Iranian national, was killed in a car bomb attack in Gol Nabi Street near the Ketabi square in northern Teheran.

Iran's semi-official Fars news agency reported that an assailant on a motorcycle stuck a bomb on the side of Ahmadi Roshan's car, killing the man and injuring two other people in the car.

Two other occupants of the car, one of them his bodyguard and driver, were wounded, Iranian media reported.

"The responsibility of this explosion falls on the Zionist regime," the deputy governor of Teheran province, Safar Ali Bratloo, told Iran's Arabic-language Al-Alam broadcaster, using Iran's term for Israel.

"The method of this terrorist action is similar to previous actions that targeted Iran's nuclear scientists," he said.

Role questioned

The attacks on Iranian scientists were viewed by Iranian officials as assassination operations carried out by Israel's Mossad intelligence service, possibly with help from US counterparts.

Wednesday's killing sharpened an international confrontation over Iran's nuclear program in which threats and counter-threats are being increasingly backed with militarized displays of muscle.

Western nations, the United States in the fore, are steadily ratcheting up sanctions on Iran with the aim of fracturing its oil-dependent economy.

Iran has responded by saying it could easily close the Strait of Hormuz - a chokepoint for 20 percent of the world's oil at the entrance to the Gulf - if it is attacked or the sanctions halt its petroleum exports.