A bomb shook the earth at a market area in northwest Pakistan tribal town near the Afghan border on Saturday, killing at least 15 people and wounding more than 20, officials said.

The blast took place in the main bazaar of Landi Kotal in Khyber tribal district, local administration official Arshad Khan said.

"The bomb exploded near a bus stand and initial reports said 11 people died and more than 20 were wounded," Khan told AFP.

Irfan Ahmed, a doctor at the state run Landi Kotal Hospital, put the toll at 12 dead.

"We have received 12 bodies and more than 20 wounded. Some are in serious condition," he said.

Khan said the blast appeared to be aimed at members of the pro-government Zakha Khel tribe, who oppose a local warlord.

Nobody claimed responsibility but Islamist militants have carried out several attacks in the area.

Pakistan is on the frontline of the US-led war on Al-Qaeda and Taliban militants, who Washington says use the semi-autonomous tribal areas as a global hub.

Since July 2007, a Taliban-led insurgency concentrated in the northwest has been fighting against the US-allied government.

In the last five years, attacks blamed on Islamist bombers have killed more than 5,000 people according to an AFP tally. AFP