Kabul: A suicide bomber attacked US and Afghan forces at a checkpoint on Wednesday in eastern Afghanistan, killing 21 people, including three US soldiers, officials said.
It was the third day in a row the Americans were targeted by insurgents as persistent violence complicates efforts to train Afghans to take over their own security in preparation for the withdrawal of most combat troops at the end of 2014.
Afghan officials initially said a car bomber struck a military convoy, but NATO spokesman Maj Martyn Crighton, said the attacker hit Afghan and coalition forces at a checkpoint in the city of Khost.
"There was a convoy in the vicinity that responded to the attack," Crighton said.
Baryalai Wakman, a spokesman for the Khost provincial government, said it appeared likely the suicide bomber was on foot.
US Defence Department officials confirmed those killed were Americans and said a suicide vest is suspected to have been used. They spoke on condition of anonymity because details of the incident were sketchy and the officials weren`t authorised to talk about it publicly.
The Afghan presidential palace said 17 Afghans also were killed when they were caught up in the massive blast. Two of the Afghan dead were police officers and the rest civilians, Wakman said. Another 32 people were wounded — all civilians, he said.
In nearby Logar province, meanwhile, seven civilians -- three women and four children -- were killed by a roadside bomb, officials said.
A tractor pulling a wagon crammed with people struck the explosives on a road outside the provincial capital earlier in the day, said provincial spokesman Din Mohammad Darwesh. Four men also were wounded in the blast, he said.