An exploding bomb or landmine killed ten young girls as they were gathering firewood outside their village in eastern Afghanistan on Monday morning, an official said.

Police said they believed that the device was an unexploded mine that had been laid years ago and was triggered somehow as the girls walked through the open field. At least one other old mine was found nearby, provincial police spokesman Hazrat Mashreqiwal said. He also noted that the blast did not occur next to a road or any obvious target.

The girls who died ranged in age from nine to 13 and all came from different families in Dawlatzai village, said Mohammad Seddiq, the government administrator Nangarhar province's Chaparhar district, which includes the vilage. Two more girls were seriously wounded and are in critical condition at a hospital, Seddiq said. He spoke to The Associated Press by phone from the site of the blast.

Afghanistan remains one of the most heavily landmined countries in the world despite years of clearance. Many mines are left in rural areas from the 1990s and discovered only when they are triggered accidentally.

A few hours later, a car bomb exploded outside of a compound housing a U.S. military contractor in the Afghan capital, blowing apart an exterior wall and wounding dozens inside, company representatives and police said.

The blast on the outskirts of Kabul sent a plume of smoke up in the air and shook windows more than two kilometres away in the city centre.

Separate explosion believed to be suicide attack

The security officer for Contrack, a McLean, Va.-based company that builds facilities for military bases, said a suicide attacker drove a vehicle packed with explosives up to the exterior wall of the compound and detonated the bomb. Afghan police said they could not confirm if it was a suicide attack or a remotely detonated bomb that had been placed in a parked vehicle.

Taliban spokesman Zabiullah Mujahid claimed responsibility for the attack, saying in an email to reporters that it was a suicide car bomber who targeted the compound because it was a company working with the government.

Contrack did not respond to calls or emails asking for comment.

Deputy Interior Ministry spokesman Najibullah Danish said that at least one person was killed in the attack. It was not immediately clear if this could have been the attacker.

Contrack security officer Baryalai, who like many Afghans only goes by one name, said he could only confirm wounded. He said the injured employees included Americans, Afghans and South Africans. An American official of the company was seriously wounded, he said.

An Associated Press reporter at the site saw large sections of exterior wall blown apart and a collapsed roof on a building inside. Twisted metal from shipping containers that had been ripped open by the explosion littered the ground. A light snow was falling all morning and was already starting to cover the debris as reporters and investigators surveyed the site. It appeared that the wall at the site of the explosion was made of mud brick — surprising in a city where most foreign contractors live in compounds reinforced by concrete blast walls.

Baryalai said the arm of the company that was attacked Monday is building barracks and other facilities for the Afghan army. Contrack's projects in Afghanistan also include fuel storage, airfield construction and tanker facilities for U.S. military bases, according to its website.

A worker coming out of the building said that he saw at least 30 people wounded.

"There was massive destruction inside ... I was sitting behind my computer when it happened. I was not hurt but I saw many of my colleagues were injured," Bashir Farhang said.

Jalalabad road, where the explosion occurred, is one of the main arteries into the city. It is flanked by a number of foreign companies and organization, along with foreign military bases.