The U.S. military in Iraq says four American soldiers have been killed during separate combat operations in Baghdad.
In statements issued Friday, the military said three soldiers were killed and 11 others wounded when a roadside bomb exploded near their patrol in eastern Baghdad late Thursday.
Earlier, the military said one soldier was killed and three wounded while conducting operations in a western section of the Iraqi capital.
Also on Thursday, at least 13 people - most of them Iraqi police recruits - were killed when a suicide car bomber struck a police station in the town of Hibhib, north of Baghdad. The attack left 15 people wounded.
Separately, U.S. Defense Secretary Robert Gates, who returned home late Thursday after a trip to the Middle East, acknowledged that U.S. officials underestimated the difficulty for Iraq's government to approve national reconciliation measures.
Gates said the "depth of mistrust" among Iraq's Sunni Arab, Shi'ite and Kurdish leaders is much deeper than anticipated.
On Wednesday, Iraq's largest Sunni Arab political bloc announced it is withdrawing from Prime Minister Nouri al-Maliki's coalition government, further undermining attempts at national reconciliation.
Some information for this report was provided by AFP and AP.