Mingora, Pakistan, Oct. 25 (Reuters): A suspected suicide bomber killed 21 Pakistanis in an attack on an army convoy on Thursday in the northwest, where a Taliban-style movement has taken root.

The bombing in the Swat valley set fire to a truck laden with ammunition a day after the military sent around 2,000 troops to the district in response to growing militant activity.

“It appears to be a suicide attack because there is no crater at the site of the blast,” Malik Naveed, commander of the paramilitary Frontier Corps in Swat, told Reuters.

A senior government official said investigators were trying to determine whether it was a car bomb or the attacker was on foot and blew himself up near the truck.

“There is a badly burnt car that hit the truck but we are not sure whether it belonged to a passerby and hit the truck accidentally or the attacker was sitting in it,” the official said on condition of anonymity.

The bodies of the victims were badly burnt. Naveed said at least 17 of the dead were soldiers.

Gul Haleem, in charge of the casualty department at a hospital in Saidu Sharif, said he had counted 21 corpses.

President Pervez Musharraf condemned the attack, the state-run Associated Press of Pakistan reported.

Witnesses said the truck caught fire after the bombing.

“When we reached near the truck it was burning. Flames were rising high into the sky. Ammunition was exploding,” resident Saeed Khan said.

Swat has seen a surge in militant activities since Maulana Fazlullah, a pro-Taliban cleric, reportedly launched an illegal FM radio calling people to jihad.

Fazlullah is de facto head of a pro-Taliban group, Tehrik-e-Nifaz-e-Shariat-e-Mohammadi, which was banned by Musharraf in January 2002.

Militants have attacked security forces and carried out bomb attacks in recent months in the scenic valley in North West Frontier Province, and have been forcing residents there to follow a strict Islamic code.