"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.
The labourers had been building a road for the US military and were sleeping in a tent in the remote area when they were killed, according to Sayed Noorullah Jalili, the director of the Kabul-based road construction company, Amerifa.
There were no survivors, he said.
The media office of the US-led coalition forces said it was trying to find out what happened.
"Something happened but we are not sure exactly what," Chris Belcher, a spokesman, said.
The province's police chief said he was trying to verify the incident.
Taj Mohammad, the head of the Nuristan provincial council, said 25 people were killed in the strike.
"We collected their flesh and put it in bags. We handed the remains of the ones we could recognise to their families," he said.
Nuristan is an isolated province on the border with Pakistan that has seen occasional fighting between security forces and the Taliban.
Several hundred civilians are believed to have been killed by foreign troops fighting the Taliban this year, but no official figure has been released.
Critics blame the military's reliance on air power in remote areas for the casualties and also accuse soldiers of disproportionate use of force.