SHAHI KOTO-- A bomb killed three U.S. soldiers and partly destroyed a girls' school in northwest Pakistan on Wednesday in an attack that drew attention to a little-publicized American military training mission in the al-Qaida and Taliban heartland.

They were the first known U.S. military fatalities in Pakistan's lawless tribal regions near the Afghan border and a major victory for militants who have been hit hard by a surge of U.S. missile strikes and a major Pakistani army offensive.

The blast also killed three schoolgirls and a Pakistani soldier who was traveling with the Americans. Two more U.S. soldiers were wounded, along with more than 100 other people, mostly students at the school, officials said.

The attack took place in Lower Dir, which like much of the northwest is home to pockets of militants. The Pakistani army launched a major operation in Lower Dir and the nearby Swat Valley last year that succeeded in pushing the insurgents out, but isolated attacks have continued.

There were conflicting reports about the source of the blast. Some officials said it was a roadside bomb detonated by remote control, while others claimed it was a suicide car bomb. (AP)