A suicide car bomb attack on a U.S. military convoy in the western city of Fallujah struck a vehicle filled mostly with female Marines, the military said early Saturday. At least two Marines were killed, including one woman, and 11 of the 13 injured were women -- the highest casualty toll for U.S. women in Iraq since the war began.

Three other Marines and a U.S. sailor who were believed to be in the same vehicle were classified as "whereabouts unknown," pending "positive identification," according to a statement released by the Marines.

The Pentagon bars women from serving in direct combat units below the brigade level. The women involved in the Fallujah incident were performing support roles. But the attack, which occurred Thursday night, underscored the continuing danger all troops face in Iraq.

According to the Marine statement, female Marines "play a vital role providing security at the entry control points" of Fallujah. "They search female Iraqi citizens moving through the checkpoints. Female Marines are employed in this role in order to be respectful of Iraqi cultural sensitivities."

The attack occurred in Fallujah's Askari neighborhood as the Marines were returning to Camp Fallujah after working at checkpoints established to control entry to the city. Two civilians -- a woman and a child -- were also killed and two were wounded, according to Mohammed Ismael, an emergency room physician at Fallujah General Hospital.

Fallujah, 35 miles west of Baghdad in the Sunni Triangle, was the scene of a massive U.S. offensive in November that wrested control from insurgents who had held the city for six months. Since the assault, U.S. forces have maintained checkpoints around the town's perimeter, as residents displaced by the fighting have returned and reconstruction efforts have been undertaken.

In a statement posted at a local mosque, the Ansar al-Sunna Army, an insurgent group responsible for many attacks on U.S. and Iraqi forces, asserted responsibility for the bombing and said it was carried out "because of the oppression of the infidel forces." In the statement, the group called on residents "not to rebuild their houses and to save the money they have in banks as we are intending to start another battle with the infidel forces."

Correspondent Jonathan Finer in Fallujah contributed to this report.

Brenda and Jerry Powell in Ouachita Parish, La. Their son, Marine Cpl. Chad Powell, died at the scene of the car bombing, the Associated Press reported.