At least 13 people were killed and over 15 others injured in a bomb attack and clashes between security forces and militants in the restive tribal belt of northwest Pakistan, officials said on Monday.

Five suspected militants were killed and one more was injured when a vehicle was targeted with a roadside bomb in Tirah Valley of Khyber tribal region, official said.

The injured man was taken to a nearby hospital, where doctors described his condition as critical.

The United States and Afghan officials describe North Waziristan Agency as a stronghold for Taliban and al-Qaeda elements.

Four militants and a soldier were killed when pro-Taliban rebels stormed a security check post in Miranshah, the main town of the lawless North Waziristan Agency, late Sunday night.

Troops in Miranshah retaliated this morning by using artillery to target suspected militant hideouts in Datakhel area but the shelling killed three civilians and injured 15 more, security officials said.