"We still have to hear exactly what they've to say ... Bagram has become the symbol of everything that has gone wrong over the past three years.

"It's caused a lot of hunger ... We still really have to hear the details about exactly what will happen there; who will be transferred and will the Americans have any kind of access or any kind of control over this detention centre.

"Still a lot of questions have to be answered."

Terrible conditions

In 2002, two detainees died after being beaten at Bagram and many people have been held for long periods without charges or trial. 

In depth

  Operation Moshtarak at a glance
  Gallery: Operation Moshtarak
  Video: Interview with US commander in Helmand
  Video: Taliban fighter says Nato losing Afghan support
  Video: Civilians flee Marjah fighting
  Focus: To win over Afghans, US must listen
  Timeline: Afghanistan in crisis

Prisoners have complained about terrible living conditions but the prison was recently revamped at a cost of $60 million.

It has been renamed Parwan Detention Facility, after Afghanistan's northern province Parwan, north of Kabul, where Bagram is located.

The centre currently houses about 700 people, "about 30" of whom are non-Afghans and "about five" are juveniles, according US military officials. 

The International Committee of the Red Cross has since 2008 organised family visits to Bagram, but they were cancelled last July amid reports of a mass protest by prisoners that went on for months.

But US military officials say the "the atmosphere has now improved".

The planned handover comes as the US prepares to launch a military offensive in Afghanistan's Kandahar city following the military operation to drive Taliban fighters out of the town of Marjah in Helmand province.

A senior US official said the impending operation would be "more comprehensive".

'Tactical prelude'

"I think the way to look at Marjah, it's the tactical prelude to larger, more comprehensive operations later this year in Kandahar city," news agencies quoted the unnamed official as saying on Friday.

Afghan troops raised their flag over Marjah as the town was symbolically handed over to the Kabul government's control after two weeks of fighting by a joint Afghan, Nato and US Marine force.

The official told reporters that the military operation was "pretty much on track", but cautioned that it would be several more weeks before Nato troops had cleared the area of Taliban fighters.

The Marjah offensive was an early test of the new strategy of Barack Obama , the US president, to send an additional 30,000 troops to Afghanistanto win control of Taliban-held areas and put in a civilian administration.

Kandahar is Afghanistan's second biggest city and has been a centre for Taliban resistance since the movement was forced from power by the US-led invasion in 2001.