CHAMAN, Pakistan -- At least 10 Afghans were killed on Friday when an ammunition depot blew up in southern Afghanistan, witnesses and officials said.

One Afghan official said a rocket fired by Al-Qaeda fugitives had hit the depot in the town of Spin Boldak, near the border with Pakistan, but another said it was too early to say what caused the blast.

"Maybe it had been due to some accident," the official said by telephone from Spin Boldak.

The roar of exploding ordnance could be heard 20km (12 miles) away in the Pakistan frontier town of Chaman, where Afghans arriving from Spin Boldak said the blast had destroyed the roofs of houses for 2km (one mile) around the site.

Witnesses said the dead included seven Afghan soldiers who were on duty at the depot and three civilians, including a girl.

"I thought it was a continuous earthquake," an Afghan who arrived in Chaman early on Friday said.

The United Nations World Food Program said six of its staff were hurt, two seriously, when what it called a projectile set off in the blast hit a warehouse it uses to store food for distribution to hungry Afghans.

"Two huge storage tanks caught fire and some edible oil supplies have been damaged. Between 600 and 800 tons of wheat supplies were saved," WFP spokesman Khaled Mansour said.

Muhammad Sharif, brother of governor Gul Agha in the Afghan city of Kandahar, told Reuters the ammunition depot had been hit by a rocket apparently fired by fugitive Al-Qaeda militants.

The militants are being hunted by U.S.-led coalition forces and Pakistani troops on both sides of the border.

An Afghan official contacted by telephone in Spin Boldak said a 2km (one-mile) area around the depot had been sealed off, but that it was too soon to say what caused the explosion.

Witnesses said a succession of explosions continued for two hours from 2.00 A.M. (2000 GMT). They said they saw several unexploded rockets scattered on roads in Spin Boldak.

"At least six of my colleagues at the depot were blown to pieces because of the explosion," an Afghan soldier, Gul Nawaz, told Reuters.

Nawaz, who was brought to the Pakistani border town of Chaman to be treated for burns, said another Afghan solider died later.

Afghan officials said the ammunition depot had been set up at a former Muslim religious seminary during operations against fugitive Taleban and Al-Qaeda militants in southern Afghanistan.

Southern Afghanistan was the stronghold of the vanquished Taleban who had sheltered Al-Qaeda leader Osama bin Laden, the man blamed by the United States for the September 11 attacks on New York and Washington.