Motorcyclists with "sticky bombs" have been blamed in several mysterious bombings of Iranian nuclear scientists. The Iranian government has blamed Israel, the U.S. and the U.K. for the deaths. Both The U.S. and the U.K. have denied any involvement.
In January, Mostafa Roshan, a director of Iran's major uranium enrichment facility, became the fifth scientist or official involved in the program killed in the past two years. He was killed by a sticky bomb placed on his car. Iran had threatened to strike back for the deaths.
Sources told ABC News Global Affairs Anchor Christiane Amanpour that it was likely Iran would use this type of "asymmetrical" warfare, and include U.S. global targets as well, if its nuclear facilities are attacked.
Sources also said Israel may be using the military wing of the Iranian exile group People's Mujahedin of Iran, or MEK, which is on the U.S. terror list, to carry out assassinations of Iranian nuclear scientists. MEK's political wing, the National Council of Resistance of Iran, is currently lobbying on Capitol Hill to have the group removed from the terror list.
In New York, police have stepped up security at the Israeli consulate, at residences and on consulate vehicles. "The NYPD adjusts its counterterrorism posture to include information about events overseas," said Deputy Commissioner Paul Browne. "That's why the public may have noticed increased NYPD presence in recent weeks at Israeli government facilities and synagogues, although there has been no specific threat in New York."
Secretary of State Hillary Clinton said she condemned the bombing and the attempted bombing "in the strongest possible terms. ... The scourge of terrorism is an affront to the entire international community."