Twelve security personnel and four civilians were killed and scores injured on Sunday in a powerful bomb attack in north-western Pakistan, a day after a suicide bomber rammed an explosives-laden car into a military convoy in the restive tribal region leaving 24 soldiers dead.

Army spokesman Major General Waheed Arshad said three improvised devises exploded on Sunday when an army convoy was heading to Matta town, some 25 km from Mingora, the largest city in the mountainous Swat valley in North West Frontier Province, the state-run PTV reported.

TV channels have put the death toll of security personnel at 12 while Arshad said four civilians were also killed in the blasts.

Besides, Arshad said, 29 soldiers were injured in the attack.

Earlier, the TV channels had said that it was a suicide attack, but the army spokesman denied such reports.

Arshad said that all the injured were evacuated from Matta and the area was cleared after the attack. The army convoy has now reached its destination, he said.

Six houses near the site of the attack were also damaged, TV channels said.

Some reports said that armed men fired at security forces from the nearby mountains after the blasts.

The government had sent soldiers to Swat and several other areas in the province to deal with the armed supporters of the pro-Taliban Lal Masjid, which was stormed by the army on July 10 to flush out militants holed up inside.