Rights groups have voiced serious concerns over the US treatment of prisoners at the Parwan detention centre [AP]

Hamid Karzai, Afghanistan's president, has demanded that the United States detention center at Bagram Air Base be handed over to Afghan control within a month, along with all Afghan citizens held by the coalition troops across the nation.

A presidential statement, released on Thursday, said that keeping Afghan citizens imprisoned without trial violates the country's constitution, as well as international human rights conventions.

The prison, inside the sprawling US base at Bagram north of Kabul, is adjacent to a well-known public detention center known as Parwan, which is run jointly by Afghan authorities and the US military.

Human rights groups have claimed that detainees were menaced, forced to strip naked and kept in solitary confinement in windowless cells.

A statement from Karzai's office said he issued instructions to a commission consisting of the ministers of defense, interior and justice, as well as other top government and judicial officials, "to complete their job regarding the handing over of the [Bagram] prison and other prisoners who are held by foreign forces".

"The work should be completed within a month,'' it said.

Political brinkmanship

The US-led NATO coalition is gradually handing over responsibility for security to the Afghan police and army. The process is due to be completed in 2014, when most foreign troops are scheduled to be withdrawn from Afghanistan.

Karzai's demands are the most recent in a series of exercises in political brinkmanship by the president, as he tries to bolster his negotiating position ahead of renewed talks for a Strategic Partnership Document with America that will determine the US role in Afghanistan after 2014.

Among the conditions that Karzai has set is an end to night raids by international troops and complete Afghan control over detainees.

The CIA's infamous secret network of "black site" interrogation centers is now gone, but suspected fighters in Afghanistan are being held and interrogated for weeks at temporary sites, including one run by elite special operations forces at Bagram Air Base.

The detainees include those suspected of having major roles in the Taliban, al-Qaeda or other armed groups.

In a separate development on Thursday, Afghan police said they arrested two British private security contractors and two Afghan colleagues after finding a cache of weapons in their vehicle. They are being held for investigation into illegal arms transport.

Karzai has ordered all the protection companies shut down by March and replaced by a unified government-run protection force.