Imad Mughniyeh, who was one of the world's most wanted fugitives, was killed in a car bomb in the Syrian capital Tuesday night. He was accused of masterminding attacks that killed hundreds of Americans in Lebanon in the 1980s.

Iranian Deputy Foreign Minister Ali Reza Sheik Attar announced the joint probe on Friday, according to Iran's official news agency.

But a Syrian official dismissed the report as "totally baseless" and said Damascus would conduct the investigation alone, Syria's state-run news agency reported late Friday. It did not name the official.

Hezbollah and its Iranian backers have accused Israel of killing Mughniyeh. Hezbollah leader Hassan Nasrallah vowed in a eulogy to the slain militant on Thursday that his Shiite guerrilla group would retaliate against Israeli interests anywhere in the world.

Israel has denied any role in the killing, and Syria has not said who it believes was behind the blast.

Iranian Foreign Minister Manouchehr Mottaki met with senior Syrian officials in Damascus on Thursday and Friday to discuss Mughniyeh's assassination. Attar said Friday that Iran and Syria agreed to the joint investigation during Mottaki's visit.

Mughniyeh was one of the most elusive and notorious Hezbollah commanders, believed to have masterminded suicide bombings in Lebanon during the 1974-1990 civil war that killed hundreds of Americans and French. He was also blamed for taking Westerners hostage and the 1985 hijacking of a TWA airliner in which a U.S. Navy diver was killed.

In the 1990s, he went into hiding, and Western and Israeli intelligence accuse him of planning suicide bombings against the Israeli Embassy and a Jewish cultural center in Argentina that killed over 100 people. Over the past 15 years, he is believed to have moved in secret between Lebanon, Iran and Syria.