Iranian authorities have arrested several suspects in connection with the assassination of nuclear scientist Mostafa Ahmadi Roshan last week, Iranian parliamentary speaker Ali Larijani was quoted as saying in Iranian media Monday."A number of people who had a hand in the assassination of martyr Ahmadi-Roshan have been arrested," Mehr News quoted him as saying. "[An] investigation is underway to identify the terrorists and details about the assassination."RELATED:'Mossad agents on the ground killed Iran scientist' Iran vows retaliation against Israel for scientist Following the assassination, Iran has accused Israel, the United States and the UK of staging the attack, the latest in a string of similar assassinations of nuclear scientists. The assassinations are believed to be part of a covert war aimed at slowing the progress of Iran's nuclear program.Ahmadi-Roshan, 32, was killed last Wednesday when men on a motorcycle placed a magnetic bomb on his car door. He was a graduate of an "oil industry university," and headed a department at the Natanz uranium enrichment facility in the Isfahan province in central Iran. "The bomb was a magnetic one and the same as the ones previously used for the assassination of the scientists, and is the work of the Zionists (Israelis)" FARS quoted Deputy Governor Safarali Baratloo as saying.On Sunday, a senior Iranian commander vowed retaliation against Israel, the US and Britain for what he described as their role in the assassination of Ahmadi-Roshan. “The opponents of [Iran's Islamic] Revolution and the nation's progress should have no doubt that the punitive response to the US, the Zionist regime (Israel) and their criminal accomplices will be delivered in an opportune time,” Iran's Press TV quoted deputy armed forces chief, Brig.-Gen. Massoud Jazayeri as saying on Sunday.The senior commander also criticized the International Atomic Energy Agency for deliberately releasing the names of Iran's nuclear scientist so that they could be located by “supporters of state terrorism.” On Friday, TIME Magazine quoted unnamed western intelligence sources as saying Israel's Mossad is responsible for training and paying the assassins of a number of Iranian nuclear scientists over the past two years.Reuters and Yaakov Katz contributed to this report.