The motive for the attack was not immediately clear, but the children studied at an elite English-language school of a type reviled by hard line militants who oppose what they as Western-imported, secular education.

The boys, aged nine to 14, were targeted in the Matani area close to Pakistan's north western tribal belt,

Suburb of Matani," senior police official Ejaz Khan told AFP."We are checking why the bus was targeted," he said.

Habib Khattak, a doctor at Peshawar's Lady Reading Hospital, said 18 wounded were admitted after the attack. Twelve of them were children, he said, with the others teachers and passers-by. The vehicle belonged to the private Khyber School, Khan said. Fee-paying,

"The gunmen were waiting for the bus in fields and attacked when it came close. They fired a rocket and then fired bullets on the van," said Kalam Khan.

Copyright AFP (Agence France-Presse), 2011