Ten Afghan civilians - including nine schoolchildren - who died in an attack in eastern Kunar province were killed by US troops, an Afghan MP claims.
Gulhar Jalal, investigating Saturday's incident for the Afghan government, said they were killed as they slept.
Hundreds of students joined protests against the deaths on Wednesday in neighbouring Nangahar province.
A coalition spokesman confirmed the operation and that some were killed, but denied they were civilians.
He said the incident was part of a joint operation alongside Afghan troops against an insurgent network that had been tracked for some time.
Impossible to verify
Troops found weapons and bomb components inside a house, the spokesman said, insisting that those killed were insurgents - not schoolchildren.
However Ms Jalal blamed US forces for launching an assault based on dubious intelligence.
"The Americans didn't co-ordinate with the Afghan government at all and relied on what their own intelligence sources told them," she said.
"They need to talk to the government and to local elders when they get such information beforehand, rather than just rely on spies who are being paid a few hundred dollars."
President Hamid Karzai has condemned the incident.
The BBC's Peter Greste in Kabul says it is impossible to verify either account. He says it is possible that both are broadly correct - and that the victims might well have been school students, but that they helped the insurgency.
Kunar province is remote, snowbound and dominated by the Taliban, so the investigation into Saturday's incident was always expected to be difficult.
Civilian deaths at the hands of foreign troops have led to widespread anger among Afghans.
President Karzai has previously said such deaths are damaging to the fight against militancy.