Baghdad, Iraq ? Roadside bombs killed three U.S. soldiers in separate attacks Monday in Baghdad and a city to the northeast, the U.S. military said, and an American civilian was shot and killed in a weekend ambush.

Also, a grenade exploded in an elementary school playground in a Shiite Muslim neighborhood of Baghdad on Monday, killing one child and wounding four others. The children apparently triggered the explosive, hidden in some garbage, while they were playing, Iraqi police said.

In the ambush Saturday, gunmen in a white sedan opened fire on a taxi carrying Americans from a religious group from the site of the ancient city of Babylon to Baghdad, the U.S. Command said in a statement. It did not identify the group, but a number of Christian humanitarian organizations are working in Iraq.

In one of Monday’s roadside bombings an American soldier from Task Force Iron Horse was killed in the center of Baqouba, 35 miles northeast of Baghdad, the 4th Infantry Division said.

Another fatal bombing occurred in the center of Baghdad about 9:20 a.m., killing one soldier from the 1st Armored Division and wounding another.

In Tall Afar, a roadside bomb exploded, killing a third soldier, the military reported today.

U.S. troops chase away Iraqi onlookers and secure the Khadimiya primary school compound in Baghdad, Iraq, after schoolchildren, playing during their recess period, accidentally detonated a grenade. One child was killed, and four others were wounded in Monday's accident.