The Pentagon bitterly attacked a decision by Afghanistan's government to release 37 "dangerous" prisoners who, it claimed, posed security threats.

Prisoner releases have been a sticking point in Afghan-US relations as the two sides struggle to reach agreement on a deal allowing US troops to remain in the country past the end of the year.

The simmering debate has involved a group of 88 detainees at the Parwan Detention Facility that the US insists pose a threat.

Earlier this month, Afghan President Hamid Karzai ordered the release of all but 16 prisoners from that group, despite the US wanting all to stand trial in Afghanistan.

The US military said that it had learned that orders had been given for the release of 37 of them.

It claimed the detainees were "dangerous insurgents with Afghan blood on their hands" and were linked to terror activities.

It said: "40 per cent have participated in direct attacks wounding or killing 57 Afghan citizens and security force members and 30 per cent participated in direct attacks wounding or killing 60 US or coalition force members."

The Afghan Review Board led by Abdul Shakoor Dadras has rejected US claims that there is enough evidence that they would return to the armed opposition.

A senior US military official said the release orders had been communicated to the US over the weekend and that Afghan officials indicated the prisoners were being moved to a building used to house those preparing to be released and reintegrated into society.

Elsewhere, Afghan authorities said a border police officer opened fire on fellow officers, killing five and wounding two at a checkpoint in western Afghanistan.

Herat Province Police General Mohammad Juma Adeel said that the dissident officer managed to escape after the shooting at the checkpoint in the Rubati Sangin district of the province.