A senior security official says the attack that killed four Americans in Libya, including the U.S. ambassador, was an organized two-part operation by heavily armed militants that included a precisely timed raid on a supposedly secret safe house just as Libyan and U.S. security forces were arriving to rescue evacuated consulate staff. 

Wanis al-Sharef, eastern Libya's deputy interior minister, said on Thursday the attacks were suspected to have been timed to mark the 9/11 anniversary and that the militants used civilians protesting an anti-Islam film as cover for their action. 

He said Ambassador Chris Stevens and another American were killed in the consulate as plainclothes Libyan security were evacuating them to the safe house. The second assault targeted the safe house, killing two Americans and wounding nearly about 30 Libyans and Americans.