Nato planes hunting Taleban militants have killed 12 men from a road building crew in Afghanistan's north-east as they slept, a provincial governor says.
The strike took place in Nuristan province, 180km (112 miles) north-east of the capital, Kabul, said Nuristan governor Tamimi Nuristani.
But Nato and US officials said a local Taleban leader "may have been killed" and the strike was legitimate.
US officials said the bombs hit a site 1km (0.6 miles) from the workers' camp.
Pentagon spokesman Geoff Morrell said the Nato forces had "acted on credible intelligence from several sources" when they launched the strike.
"We believe that Abdullah Jan, the western Nuristan Taleban commander, may have been killed in the air strike. We deem it, at this point, a legitimate air strike.
"There were no structures, vehicles or any other construction equipment within the vicinity of the impact area," said Mr Morrell.
The governor of Nuristan and the head of the Amerifa Construction Company said his workers had been killed in the incident, which took place late Monday.
"I don't think the Americans were targeting our people," said Amerifa director Sayed Nurullah Jalili.
"I'm sure it's the enemy of the Afghans who gave the Americans the wrong information."
Governor Nuristani told AFP news agency: "We had reports that rebels were there.
Jaap de Hoop Scheffer said Nato had changed its tactics
"There was an air strike by coalition forces but later we found out that 12 people, all local road workers, were killed.
"The road workers were in a tent which was hit by one bomb. All died," he said.
Nato has come under increasing pressure over Afghan civilian casualties.
Last week, Nato head Jaap de Hoop Scheffer had said the organisation was doing all it could to avoid Afghan civilian casualties.