A blast in a northwest Pakistani town has killed 17 people aboard a bus, officials say.

The explosion, which happened on Monday morning near the town of Kohat, also injured 11 other passengers.

Police said that the minibus had been planted with about 10km of explosives.

"The report of the bomb disposal squad shows that explosive materials fitted with a timer were placed near the gas cylinders which caused the explosion," Abdul Rashid, district police chief, told AFP from the scene.

"The death toll has risen to 17 and five bodies still remain unidentified, as they have have been burnt very badly," he added.

The mangled and burned-out wreckage of the minibus and another passenger vehicle were left at the scene.

Rashid said most of the passengers in the minibus had been killed, along with two people travelling in a pick-up truck nearby when the blast occurred.

Bus carnage

Senior police official Masood Khan Afridi confirmed that the blast was caused by high-intensity explosives.

"We are looking for the owner of the vehicle, as the driver was killed in the blast," he said.

Local television footage showed the twisted carcass of the bus laying beside the road with little left except its wheels and undercarriage.

Another bus nearby was flipped over on its side with its windows blown out and blood splattered across the outside.

Pakistani Taliban have carried out numerous suicide bombings and other attacks on soldiers, security forces and police in a bid to destabilise the US-backed government.

The government has said military offensives have weakened the Taliban - who are reportedly linked to al-Qaeda - but fighters often move around and establish new strongholds after being dislodged.

Aside from facing a resilient force of Taliban fighters, the government is under pressure from the United States, the source of billions of dollars in aid, to help its efforts to stabilise Afghanistan.

Source: Agencies