Separate insurgent attacks have killed two U.S. soldiers since Wednesday morning, the military announced Thursday.

Also, two rockets hit the Ishtar Sheraton Hotel Thursday evening, a hotel in central Baghdad that houses many contractors and journalists. No casualties were reported, but the attack started a fire in the building, shattered windows and caused damage outside.

Security forces responded with automatic weapons fire.

One 1st Infantry Division soldier was killed and a civilian interpreter wounded about midnight Wednesday when their patrol was attacked by small arms fire and a roadside bomb near Baiji in northern Iraq, according to a statement from the military.

At 9:45 a.m. Wednesday, a U.S. soldier was killed near Fallujah in an attack on an Army convoy near the rebel-controlled city of Fallujah.

A news release on the incident said only that the convoy was hit by an "unknown type of explosive device." Two other soldiers were wounded in the Fallujah attack.

American forces have been conducting regular airstrikes on Fallujah for weeks in an attempt to disrupt insurgent forces holed up in the Sunni triangle city west of Baghdad.

The Katyusha rockets that hit the Sheraton were fired from a vehicle, Col. Adnan Abdul-Rahman, an Interior Ministry spokesman, told the Associated Press.

Security sources also said the U.S. military was investigating the possibility of bombs in the vicinity.

The initial attack hit a room on the first floor that is used by U.S. soldiers, who are stationed here to help provide security for the American contractors who live at the Sheraton. No one was in the room at the time. The second rocket hit a room on the fourth floor.

The attack came just hours after U.S. officials warned of a possible threat to the Green Zone in Baghdad, the area across the river from the Sheraton that is cordoned off because it includes the U.S. Embassy and Iraqi government offices.

Barbash reported from Washington. Staff writer Lexie Verdon contributed to this story.