The mysterious killing of an Iranian nuclear scientist this week has led to speculations about the real motives behind these coordinated operations. This latest is the fourth of its kind in the past two years.

As the news of the assassination broke out, a number of well-known pro-Iran lobbyists started to blame Israel, the U.S. and the main Iranian opposition group the Mujahedin-e Khalq, MEK, for the killing.

Richard Silverstein an American-Jewish blogger who supports Iran's nuclear ambitions to be "legitimate" got the headlines in Iran's state-run media. The assassination was a "joint Mossad-MEK operation," he wrote. The story was based on an uncorroborated claim by his "confidential Israeli source". A similar thing happened in November 2011 when an explosion at a base of Iran's Revolutionary Guards killed 17 Guards members. Silverstein then claimed that explosion was a joint venture by the Mossad and MEK. His only proof was an unnamed Israeli source. When pressed whether his 'source' had ever broken such stories before? Silverstein replied "I'd rather not be more specific."

Trita Parsi, a U.S.-based Iranian lobbyist with well-established links to Iran's authorities, who helped the regime launching a massive campaign to maintain the MEK on U.S. Terror list last summer, was quoted in the Iran's state-run media, parroting the claim of a joint Israel-MEK operation.

European Courts tasked with investigating the terror designation on MEK, having looked through all secret materials, did not find evidence linking the MEK with any violent acts since they had declared an end to military operations in 2001.

Iran has a long record of orchestrating media campaigns to spread misinformation and rumours targeting its opposition. In some cases media outlets have been offered six-figure sums to publish a story against MEK.

US Secretary of State Hillary Clinton "categorically" denied any U.S. involvement in this latest incident.

The MEK for their part rejected any role. "Attributing murder of the mullahs' regime nuclear scientist to the PMOI is absolutely false", a statement from Paris based umbrella organisation NCRI which the MEK is a party of stressed.

In 2002, NCRI was first to blow the whistle on Iran's secret nuclear ambitions which had been kept secret from western intelligence for 18 years. The information proved accurate. Several Iranian scientists were later arrested and executed by the regime for having passed that information to NCRI.

Iran's leaders are now suspected in quietly eliminating potential discontented nuclear scientists for double gains: preventing further leaks of their nuclear weapons program, while portraying themselves as victims to western insurgency and accusing their opposition for terrorism.

Iran's supreme leader Ayatollah Khamenei had ordered a special unit of the Revolutionary Guards that "as soon as a sign is detected that a nuclear experts is distancing from the regime or has the intention of leaving the country, he should be eliminated and the blame should be put on the MEK, agents of the U.S., Israel, and World Arrogance," the NCRI statement revealed.

Ironically, four days before this latest assassination, the Director of Iran's Atomic Organisation told the state-run Fars news agency: "we shouldn't be ignorant that as soldiers fled the battlefield during the war, in the scientific war there are also scientists who, for the sake of preserving their international connections, refuse to cooperate in (our) nuclear projects.... Of course we have never been worried about this since there is plenty of human resources and experts in the country."

The timing of this latest assassination becomes more intriguing as some fear it could be used to justify the execution of an Iranian-American former U.S Marine, sentenced to death earlier this week on charges of espionage, despite statements by him, his family, and the U.S. government that he is not a spy.

While few would shed any tear on Iran's leaders losing their nuclear capability, it is important to differentiate facts from fiction as one could easily end up dancing to the mullahs' tune.