Updated

Nine U.S. soldiers died in two separate incidents north of Baghdad, the military said Tuesday.

Six American soldiers died when a bomb exploded Monday near their vehicles during a combat operation in Salahuddin province, the military said. Three others were wounded in the blast. Another three soldiers died the same day in a roadside bomb attack in Diyala province northeast of Baghdad.

Both provinces are Sunni-dominated and have seen a rise in violence since additional U.S. forces surged into Baghdad as part of a security crackdown three weeks ago.

Monday was "a very traumatic day" for U.S. troops in Iraq, said Lt. Col. Michael Donnelly, a spokesman for U.S. forces in northern Iraq.

"Our hearts and prayers are with the families right now in their time of loss, and our resolve is stronger to accomplish our mission here," Donnelly said.

It was the deadliest day for Americans in Iraq since Feb. 7, when 11 troops were killed — seven when their helicopter was shot down north of Fallujah and four others in combat operations.

The highest daily U.S. death toll since the Iraq war began was Jan. 26, 2005, when 37 Americans died in attacks.

U.S. officials say as violence has fallen in Baghdad, where the joint U.S.-Iraqi security crackdown was in its third week, insurgents have fled the capital for outlying areas, such as those where the soldiers were killed Monday.