The recent bombings end a relative lull in militant violence over the past month and turn up the heat on a government overwhelmed by devastating floods that have made millions homeless and hammered the economy.

Nearly 100 people were killed last week in suicide bombings on processions of minority Shi'ite Muslims in the eastern city of Lahore and southwestern city of Quetta.

Pakistan's Taliban claimed responsibility for Monday's attack in the town of Lakki Marwat, warning the government not to use lashkar, or militias, to fight the group.

The bomber struck a school van before hitting the rear wall of the police station. The blast turned most of the police station into rubble. Burned-out cars were flipped on their sides.

"Nineteen people have been killed. There are nine policemen and two children among the dead," said the Information Minister of Khyber-Pakhtunkhwa province, Mian Iftikhar Hussain.

Hussain said 34 people, including 20 policemen, were wounded.

The United Nations said on Monday it needs double the initial US$460 million in aid to help victims of the flood in Pakistan.