US officials say the assassinations of Iranian nuclear scientists have been carried out by an Iranian opposition group with logistical and financial support from the Mossad, NBC News reported Thursday.The report was based on testimony from one of Iranian Supreme Leader Ayatollah Ali Khamenei’s senior advisers, who described an intimate relationship between Israel and the opposition group MEK (the People’s Mujahedeen of Iran) that “two senior US officials” confirmed as accurate.NBC quoted Khamenei’s aide Muhammad Javad Larijani as saying, “They [the Israelis] are paying... the Mujahedeen. Some of [MEK’s] agents... [are] providing Israel with information.And they recruit and also manage logistical support.”Larijani explained that because Israel did not have “direct access” to Iran, the Mossad was working with the dissident group, which operates in Iran and also has agents in Iraq.One of the two senior US officials who reportedly confirmed the Iranian accusations said that all the “inclinations” in Larijani’s remarks were “correct.”Khamenei’s aide said Iran’s proof of Israeli involvement was based on the interrogation of an assassin who had unsuccessfully attempted to carry out a similar attack, and the “materials found on him,” according to the report.Despite Iran implicating the CIA in the most recent assassination – that of nuclear scientist Mostafa Ahmadi Roshan, 32, near Tehran University – the officials denied any US involvement in the attack.The Foreign Ministry declined to comment, saying it would not “react to every gossip and report being published worldwide,” according to NBC.Iran believes Israel wants to kill its nuclear scientists to thwart its controversial nuclear program, which Israel believes is aimed at developing a nuclear weapon.While it did not respond to NBC’s report, MEK summarily denied any involvement in the assassination of Iranian scientists after Roshan was killed by a bomb a passing motorcyclist latched to his car.The US has long designated MEK as a terrorist organization, since it killed American personnel in Iran in the 1970s and supported the takeover of the US Embassy there following the Islamic Revolution.