Eight Iraqi soldiers have been killed and six wounded in a US helicopter strike in the northern Iraqi city of Mosul, local officials have said.
The officials described Friday's incident as an act of "friendly fire", which hit an Iraqi army position in the east of the city.
The US military said five men were killed, and said the intended target had been a suspected al-Qaeda cell.
It expressed its "deepest sympathies" to the families of the dead.
The Kurdish officials said US helicopters hit the men who were guarding a branch of the Patriotic Union of Kurdistan (PUK) in Mosul.
They said the victims were all Kurdish.
Iraqi President Jalal Talabani, who leads the PUK, was concerned about the incident and wanted more details about what happened, his spokesman was quoted as saying by Reuters news agency.
The US military said the attack was launched after its soldiers had identified armed men in a bunker near a building that was reportedly used for bomb-making.
The troops called for the men to put down their weapons in Arabic and Kurdish, before launching the strike, the US said.
One local official told the BBC that the victims were Peshmerga fighters.
Peshmergas spent decades resisting the Saddam Hussein regime.
Many joined the Iraqi army after he was ousted.