The World - 21 killed in attack on Pakistani army convoy

The attack, representing a new challenge to President Pervez Musharraf's government, came less than a week after nearly 140 people were killed in an attack on a crowd gathered to welcome former Prime Minister Benazir Bhutto on her return to Pakistan. No group has claimed responsibility, but investigators believe militants linked to the Taliban or Al Qaeda carried out the twin bombings.

The blast Thursday in the picturesque Swat valley hit a military truck that was loaded with ammunition, setting off huge secondary explosions. Authorities believed the attack was carried out by a suicide bomber in an explosives-laden vehicle, but they had not ruled out the possibility of a roadside bomb.

Nearly all of those killed were paramilitary troops, but at least four civilian bystanders were among the dead, military officials said. Dozens of people were injured.

The convoy was traveling through a high-security zone in Mingora, the main town in the Swat district, on its way to the headquarters of the paramilitary Frontier Constabulary. Witnesses said injured soldiers, uniforms aflame, leaped from the truck, and that the force of the blast set fire to more than a dozen shops and a gasoline station.

This week, the government deployed about 3,000 army and paramilitary troops to Swat, where forces loyal to radical cleric Maulana Fazlullah have been seeking to impose a Taliban-style code of law.

The presence of militants in Swat, in Pakistan's North-West Frontier Province, is a relatively recent development, a spillover from the lawless tribal areas bordering Afghanistan where the Taliban and Al Qaeda, together with local militants, have ensconced themselves.

Fazlullah, who reportedly went into hiding when the government troops moved in, has been using a pirate radio station to rally his followers, calling on them to wage holy war against Musharraf's government. Fazlullah heads a group, banned by the government in 2002, that advocates the imposition of a strict version of Sharia, or Islamic law.

Musharraf condemned the bombing as a "dastardly terrorist attack," Pakistan's state-run news agency reported.