The United States is investigating reports that hundreds of Taliban prisoners died at the hands of their Afghan captors after surrendering in northern Afghanistan last November.
Newsweek magazine reports that the prisoners died of suffocation in overcrowded container trucks as they were taken from their former stronghold of Kunduz to a prison in the town of Sheberghan.
The report follows revelations in May that a human rights organisation had found mass graves outside Sheberghan earlier in the year.
The American State Department said Washington would ensure that the Afghan authorities were held accountable for any violations.
A spokesman for the Department said there was no indication that US forces had knowledge of such incidents.
