BAGHDAD, Iraq — Three U.S. soldiers were killed in a mortar strike on a U.S. base in the restive western city of Ramadi, and another died in a bombing outside Baghdad, authorities said yesterday.

The insurgent mortar attack late Saturday also injured seven others at a U.S. base in Ramadi, a Sunni stronghold that has been among the most violent places in Iraq. The assailants fled into a nearby mosque, a U.S. statement said.

Another U.S. soldier died yesterday south of Baghdad after being wounded by an improvised bomb, Reuters reported.

Attacks against U.S. forces have declined since the Iraqi election, officials say, but at least six U.S. troops were killed in separate attacks over the weekend.

As of yesterday, at least 1,554 members of the U.S. military have died since the beginning of the Iraq war in March 2003, according to an Associated Press count.