Gates says markings tie bombs to Iran

Serial numbers and other markings on bombs suggest that Iranians are linked to explosives used by Iraqi militants, Defense Secretary Robert M. Gates said.

Speaking with reporters in Seville, Spain, before traveling to Munich, Germany, Gates said the markings provided "pretty good" evidence that Iranians were supplying weapons or technology for Iraqi extremists.

Gates' remarks left unclear how the U.S. knows the numbers are traceable to Iran and knows too that such weapons were sent by the Iranian government rather than private arms dealers.