Insurgents attacked American troops and Iraqi security forces north of Baghdad (search), sparking fierce overnight battles that killed at least 40 Iraqis and wounded several soldiers, a U.S. military spokesman said Saturday.

The fighting in Baqouba (search), 30 miles northeast of Baghdad, began with simultaneous rocket attacks late Friday on an Iraqi police station, the governor's office and a compound housing the U.S. military's civil affairs office, said Capt. Issam Bornales, spokesman for the 1st Infantry Division's (search3rd Brigade.

The assailants opened fire with rocket-propelled grenades and rifles, sparking small fires in each location. Fighting quickly spread throughout the city of 26,000 people.

"This was a well-coordinated attack in certain areas, but in others just ordinary frustrated people seemed to come out and take some shots at American soldiers," Bornales said. "It's hard to separate the wheat from the chaff."