As Iran has long claimed, Israel is indeed behind the assassinations of Iranian nuclear scientists, providing financing, training, and weapons to the Iranian terrorist group that carries out the attacks, US officials confirm to NBC News. Five Iranian nuclear scientists have been killed since 2007, reportedly by the People’s Mujahedin of Iran (MEK). That group of dissidents—which was accused of killing American servicemen in the 1970s—is backed by the Mossad, Israel's secret service. "This is an Israeli plot. A dirty plot," says a senior aide to Iran's supreme leader Ayatollah Ali Khamenei, who adds that most of the Iranian government's information came from the interrogation of an MEK member whose attempted attack failed in 2010.
Anonymous US officials confirm that the White House is aware of the campaign but is not directly involved, although one of the three senior officials cited would neither confirm nor deny. According to the senior aide, Mossad agents train MEK members to use motorcycles and small bombs, and even once built a replica of a scientist's home so assassins could learn the layout. There are also unconfirmed reports that Mossad and the MEK were involved in the November explosion that destroyed an Iranian missile research and development site, and one expert says the two groups may have collaborated on other attacks. Click for the full report, which has much more on the US-MEK relationship. (Read more Iran nuclear weapons program stories.)