Mossad officials are training Iranian dissident activists to assassinate Iranian nuclear scientists, a NBC News report citing U.S. officials said on Thursday. The report noted, however, that Washington was not directly involvement in the alleged attacks.

The report by NBC News followed Iranian accusations that Israel and the U.S. had been orchestrating attacks against Iranian scientists and military officials associated with Iran's nuclear program.

Open gallery view Ahmadi Roshan's car following the explosion in Tehran, January 11, 2012. Credit: Fars News Agency

These accusations resurfaced following the most recent alleged attack, as Iranian media reported last month that nuclear scientist Mostafa Ahmadi-Roshan was killed by a bomb placed on his car by a motorcyclist in Tehran.

According to the semi-official Fars news agency, Ahmadi Roshan, 32, supervised a department at Natanz uranium enrichment facility in Isfahan province.

The United States has denied involvement in the killing and condemned it. Israel has declined to comment.

Just days following the bombing, Foreign Policy, quoting U.S. intelligence memos, reported that Mossad agents posed as CIA officers in order to recruit members of a Pakistani terror group to carry out assassinations and attacks against the regime in Iran.

Open gallery view Funeral of of Mostafa Ahmadi Roshan, a chemistry expert and a director of the Natanz uranium enrichment facility in central Iran, who was killed in a brazen daylight assassination. Credit: AP

Foreign Policy's Mark Perry reported that the Mossad operation was carried out in 2007-2008, behind the back of the U.S. government, and infuriated then U.S. President George W. Bush.

Later, a Sunday Times report claimed that agents associated with Israel's secret services were behind Ahmadi Roshans' assassination of an Iranian nuclear scientist.

On Thursday, U.S. officials speaking to NBC news claimed that Mossad agents were training members of the dissident terror group People’s Mujahedin of Iran in order assassinate Iranian nuclear scientists, adding that the administration of U.S. President Barack Obama was aware of the operation, but had no direct link to them.

The U.S. officials reportedly confirmed the link between Israel and the People’s Mujahedin of Iran (MEK), with one official saying: "All your inclinations are correct.”

Yet another American official would only tell NBC “It hasn’t been clearly confirmed yet.” All officials in question denied any U.S. involvement.

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A Foreign Ministry comment to the story said that as "long as we can't see all the evidence being claimed by NBC, the Foreign Ministry won't react to every gossip and report being published worldwide."

The NBC report also cites a senior aide to Iranian Supreme Leader Ayatollah Ali Khamenei as describing what he said were strong links between Israel and Iranian dissident groups.

Mohammad Javad Larijani is quoted as saying that the these relations are "very intricate and close."

"[Israelis] are paying … the Mujahedin. Some of their (MEK) agents … (are) providing Israel with information. And they recruit and also manage logistical support,” the reported quoted Larijani as saying.