Washington: Three US civilian contractors were among those killed by a car bomb that targeted their NATO convoy, the US-led coalition in Afghanistan said, making the attack that killed 12 people one of the most lethal to target US citizens in recent years.
The blast destroyed several vehicles, including a school van and an armoured pick-up truck believed to be used by the contractors which was left twisted and blackened.
"One Resolute Support U.S. contractor was killed and two Resolute Support US contractors died of wounds," the NATO coalition known as Resolute Support said in a statement late on Saturday.
Most of the dead were Afghan civilians and scores more were injured in the suicide attack outside a hospital on a busy residential street, heightening the anger felt in Kabul after a string of deadly blasts that killed dozens this month.
The Taliban, who are fighting to re-establish hard-line Islamist rule more than 13 years after the U.S.-led military intervention that toppled their regime, denied it was behind the attack. No group has claimed responsibility.
The U.S. embassy in Kabul condemned the bombing.
"The United States remains committed to assisting our Afghan partners in their efforts to ensure a peaceful future," it said in a statement.
The violence has strained Afghanistan`s ties with neighbour Pakistan, with Afghan President Ashraf Ghani accusing the Pakistan government of not doing enough to stop militants planning attacks from training camps he says lie across the border.
The official anger has spilled on to the streets, with protests against Pakistan`s alleged involvement in the recent bloodshed, including people burning the Pakistani flag and a campaign to boycott Pakistani products.
Saturday`s blast blew glass blown out of the windows of the Shinozada hospital and a six-storey building opposite. On its website, the Shinozada is described as Afghanistan`s first private hospital.