Three U.S. soldiers traveling with Pakistani security forces were killed Wednesday in a roadside bomb blast in northwest Pakistan, officials said.

U.S. troops don't typically operate inside the country. However, these soldiers were there as part of a little-publicized mission to train local security forces in the fight against al Qaeda and the Taliban.

The bomb, which left at least four others dead and approximately 70 injured, struck a security convoy not far from the Afghan border.

Pakistani officials said students from a nearby girl's school were among the wounded.

"What was the fault of these innocent students?" said Mohammed Dawood, a resident who helped police dig the injured from the rubble.

The U.S. has recently ramped up its missile strikes in the area, dealing a heavy blow to the terrorists.

The U.S. Embassy has yet to comment on Wednesday's attack. But the deaths, if confirmed by U.S. authorities, would represent a major victory for the region's militants.