At least 16 people, including five police officers, have been killed after a vehicle loaded with explosives rammed into a mosque in north-western Pakistan, according to a senior police official in Peshawar.

A gun battle is still ongoing between attackers and security forces at the site in the Kohat district of Khyber Pakhtunkhwa.

One of the assailants has reportedly been killed, an officer says, and a rescue operation is under way.

In a statement, Pakistan's President Asif Ali Zardari expressed "his best wishes for the swift recovery of those injured in the explosion."