Pakistan's military says three U.S. soldiers traveling with Pakistani security force members were among at least 10 killed in a roadside bombing near a girls' school in northwest Pakistan.
Schoolchildren were reportedly among the dead.
Pakistan's Taliban have claimed responsibility for the bombing and threatened more attacks.
"We will continue such attacks on Americans," Taliban spokesman Azam Tariq told Reuters by telephone from an undisclosed location.
According to unnamed Pakistani officials, the three U.S. soldiers were in the region as part of a small, little-publicized U.S. mission to train members of the paramilitary Frontier Corps to better fight Al-Qaeda and Taliban militants.
The blast hit a convoy close to the girls' school, celebrating its opening in the Shahi Koto area of Lower Dir district.
At least 70 people, including more than 60 school girls, were injured in the explosion.
The U.S. Embassy declined to comment.
compiled from Reuters and other agency reports