WASHINGTON — The deadly bombings outside the American embassy in Yemen today were carefully orchestrated, with sniper fire and some attackers apparently dressed as soldiers, a senior U.S. official said. The White House called the attack a reminder of the danger from “violent extremists both at home and abroad.”

As many as five explosions struck the embassy, and Yemeni authorities who first responded were ambushed by snipers, said the official, who spoke on condition of anonymity to describe internal Bush administration briefings.

The official said all American personnel are safe and accounted for. One locally employed embassy security guard was killed in the attack, as well as four Yemeni troops guarding the embassy and five other people, the official said.

He said it appeared some of the attackers were dressed as Yemeni troops and that the first Yemeni emergency personnel to arrive on the scene were hit by heavy sniper fire from gunmen who had stationed themselves across the street from the embassy.

The White House condemned the attacks and offered condolences to the families of the victims.

“This attack is a reminder of the continuing threat we face from violent extremists both at home and abroad,” said White House spokesman Gordon Johndroe.

“We will continue to work with the Government of Yemen to increase our counterterrorism activities to prevent more attacks from taking place,” he said.