A forgotten Soviet-era landmine has killed 10 Afghan schoolgirls and seriously injured another in a grim reminder of the ongoing impact of decades of war on the country.

The girls, all under 12, spent their mornings collecting wood to help their families through the bitter winter, and went to school in eastern Nangarhar province in the afternoon.

They were unwittingly gathered round a long-buried landmine, splitting logs with a small hatchet, when the blows detonated the old explosives, said provincial police chief General Abdullah Stanekzai. "The bomb was from Russian times, and the girls were collecting wood and trying to break the wood, but underneath it was the bomb," Stanekzai said.

Nine died instantly and one other died in hospital, where an 11th girl is battling for her life. Just one of the group escaped unharmed. "We found another two bombs at the site and defused them," Stanekzai added.

The bomb went off in an area of low, forested slopes where the girls gathered wood every morning, said the spokesman for Nangarhar province Ahmad Zia Ahmadzai, who confirmed the death toll.

Afghanistan is one of the most heavily mined countries in the world, despite years of programmes to clear the land. Children are often victims of forgotten bombs as they play or work in remote rural areas. They also suffer badly from the current conflict; nearly one in five civilian casualties in the first half of this year were children, the United Nations said.

"It was a British-made anti-tank mine," Abigail Hartley, the manager of the UN mine programme in Afghanistan, told the Associated Press. She said there were not enough pieces of the exploded mine to determine its exact make, but that two MK7 British mines were found nearby, so they assumed it was a similar mine that exploded.

"I was having breakfast when I heard a bang. I came out of my house to see what had happened," villager Jan Mohammad told Reuters. "Later I carried three of the wounded children to the public health centre."

They were buried the same day, in accordance with Islamic tradition. Photographs from the ceremony showed a crowd of relatives and neighbours praying round a poignant line of graves marked only by rough slate headstones.

The tragedy came on the same day that a truck bomb in Kabul killed two civilians working for a US military contractor and wounded at least 15 others, and gunmen murdered an employee of the education ministry in southern Kandahar province.

Kabul's police chief General Ayoub Salangi declined to say if the explosion in the capital was a suicide bombing or a car bomb detonated remotely. The bomb went off by the wall of a compound belonging to Contrack, a US company that builds facilities for military bases, injuring Afghan and foreign employees and killing two Afghans.

The Taliban claimed responsibility for the attack, saying the compound was targeted because the firm was working with the government.

In Kandahar the education ministry employee was killed by gunman as he was heading from work to classessaid Sher Agha Safai, head of the provincial education department.