An explosives-laden pickup truck blew up in front of a police station in northwestern Pakistan on Monday, killing at least four people and wounding 30 others.

The blast in the town of Badh Ber damaged the police station and a mosque, and destroyed several homes and shops.

Police opened fire on the truck as it approached a checkpoint in front of the station, but the driver of the vehicle was able to detonate the estimated 250 kilograms of explosives that were in the truck.

Badh Ber is about 12 kilometres south of Peshawar. The area has seen a surge in violence since Pakistan launched a military offensive against militants in South Waziristan region in mid-October. More than 300 people have died in attacks by suspected militants since the military operation began.

"We have to continue this war against terrorists and have to keep our nerves," said Mian Iftikar Hussain, the information officer for North West Frontier Province, where Badh Ber is located.

Hussain said the South Waziristan military operation has driven many militants out of the semi-autonomous region into areas near Peshawar.

"Terrorists have spread into our settled areas and have surrounded Peshawar, but they cannot defeat our resolve," he said.