Bombers riding motorcycles killed one of Iran's top nuclear scientists and wounded another in separate attacks on Monday, escalating tensions over Tehran's controversial nuclear program. The man killed, Majid Shahriari, was running a "major project" at Iran's Atomic Energy Agency, and the wounded man, Fereydoon Abbasi, may be even more important: He was placed on a United Nations' sanctions list for his ties to Iran's nuclear effort. Iranian President Mahmoud Ahmadinejad has blamed the U.S. and Israel for the violence. Is this really the handiwork of Western spies, or is someone else targeting Iran's nuclear scientists? (Watch an AP report about the attacks)

Iran is right — Israel did it: "It is obvious," says Yossi Melman in Britain's Independent, that this was part of Israel's "endless efforts" to "sabotage, delay and if possible, to stop Iran" from building a nuclear bomb. Israel's intelligence agency, Mossad, is known for using motorcycles, and, along with its allies in the CIA, has demonstrated that it will use every means to disrupt Israel's nuclear program, including a recent computer-worm attack on the nuclear computers at Natanz.
"Mossad, MI6, the CIA and the case of the assassinated scientist"

This was more likely an inside job: It's "just as feasible" that the Iranian regime itself carried out the attacks, says Hugh Tomlinson at The Australian. When Iran blamed Israel for the assassination of another nuclear expert, Massoud Ali-Mohammadi, in January, it turned out he was a sympathizer with the reform movement. If the two new victims, who shared professional ties with Ali-Mommadi, were closet reformists, "the regime could have attacked them to prevent them from leaking secrets."
"Iran 'behind scientist killings': Analysts"

Iran's neighbors also had motive, and intent: There are plenty of suspects, says Ed Morrissey at Hot Air, including "Saudi Arabia, Egypt, or perhaps even Iraq, which would find itself under the Iranian thumb more quickly than anyone if Tehran gets a nuke." It probably wasn't the U.S., where an Executive Order forbids assassinations, but it might have been Iranian opposition groups "wanting to get out from under the mullah's thumb." The truth is, no one knows. This is a regular "Agatha Christie whodunit."
"Iranian nuclear scientists targeted in bomb attacks, one dead"