Afghan officials: US missiles killed 27 civilians

Karzai suggested that Afghan civilians may have been fleeing at the time of the strike because of a warning from the U.S. coalition.

"Coalition forces are saying that this operation was against armed insurgents in the area, but Gov. Nuristani is insisting that three hours before this airstrike, people were informed by international forces that they should leave the area because of a possible airstrike against insurgents," Karzai said in a statement.

Elsewhere, in the southern province of Helmand--the country's other hotly contested region--a clash killed seven Taliban and two police, provincial police Chief Mohammad Hussein Andiwal said. Five other officers were wounded during the Saturday fight in Nawa district, he said.

The coalition said several militants were also killed Friday during an operation in Ghazni province.

More than 2,100 people--mostly militants--have been killed in insurgency-related violence in Afghanistan this year. More than 8,000 people died in attacks last year, according to the U.N., the most since the 2001 U.S.-led invasion.

The number of militant attacks has been on the rise this summer compared with the same period last year, NATO officials say.