ISLAMABAD, Oct. 9 (Xinhua) -- At least eleven people, including four students and five policemen, were killed when a bomb blast apparently targeting policemen took place in northwestern Pakistanon Thursday, police said.

    A police van carrying prisoners hit a roadside bomb in Upper Dir district of North West Frontier Province, and the blast also affected a school bus passing by.

    The blast has left eleven people dead, including four students, five policemen and two prisoners, local Geo TV channel reported.

    There is no further information about the attack, for which no group claimed responsibility.

    Earlier on Thursday, a blast also took place near heavy-guarded police complex in Pakistan's capital, injuring at least ten people.