Media playback is unsupported on your device Media caption A video shows Sgt Bowe Bergdahl being handed over to US forces

The Taliban have released a video showing the moment Sgt Bowe Bergdahl was handed over to US forces after five years in captivity in Afghanistan.

The footage shows him sitting in a pick-up truck, before being walked to a helicopter in a Khost province valley.

The US soldier was freed on Saturday in exchange for the release of five senior Taliban figures from Guantanamo Bay.

The deal has caused controversy in the US, with Republicans warning it could put American lives at risk.

The video, released on Wednesday, shows the soldier dressed in traditional Afghan clothing as he sits waiting in the truck.

Several armed men with covered faces are seen standing next to the vehicle and on the hillside.

A Black Hawk helicopter then lands and the Taliban fighters - one of whom carries a stick with a white flag - lead Sgt Bergdahl to a meeting point where he is being taken away by US forces.

The exchange took place in Ali Sher district of Khost province near the Pakistan border.

Bilal Sarwary, BBC News, Kabul

Local sources in Khost have told the BBC that members of the Haqqani network handed over Sgt Bowe Bergdahl in the remote valley of Betani, 40km (25 miles) from Pakistan's Waziristan region.

The area is controlled by the group and its commander, Mullah Tajmir, who served as a senior intelligence official during the Taliban regime, and has close ties to Sirajuddin Haqqani and Taliban leader Mullah Omar.

The US has long described the Haqqani group as a major threat. The network - which has also links to al-Qaeda - has carried out a series of high-profile attacks against foreign troops in Afghanistan. The Pakistan-based militant network was designated a terrorist group by the US in 2012, making it subject to sanctions.

Image copyright Reuters Image caption Sgt Bowe Bergdahl is seen sitting in a pick-up truck guarded by armed men

Image copyright Reuters Image caption The US soldier, who was captured in Afghanistan in 2009, appears slightly dazed in the video

Image copyright Al-Emara Image caption The moment Sgt Bergdahl is being handed over to US forces in Khost province

Image copyright Reuters Image caption The US Army said it would investigate the circumstances surrounding his capture

Since Sgt Bergdahl's release, a growing chorus of opposition Republicans have criticised President Barack Obama's decision to agree to the prisoner swap.

They have described it as a deal with terrorists, and say the transfer of five Taliban senior prisoners from the detention facility at Guantanamo Bay, Cuba, to Qatar, endangers Americans.

Some also accused Mr Obama of contravening a law requiring the White House to notify Congress 30 days in advance of any transfers of prisoners from Guantanamo.

But the president has defended his decision, saying America had a "pretty sacred rule" not to leave soldiers behind.

"We don't leave our men or women in uniform behind and that dates back to the earliest days," he said.

The administration has argued that delaying the soldier's transfer to comply with congressional rules could have put the deal at risk.

Image copyright AP Image caption The soldier's parents, Jani and Robert Bergdahl, have tirelessly campaigned for their son's release

Image copyright AP Image caption Residents in Sgt Bowe Bergdahl's hometown of Hailey, Idaho, have heralded his release from captivity

The circumstances of Sgt Bergdahl's capture in 2009 remain unclear, although the Pentagon has concluded he left his post in Paktika Province without authorisation.

In the days following his release, a number of conservative commentators and former US soldiers have branded him a deserter and called for him to be punished.

And critics of the deal have alleged that six US soldiers were killed in the initial efforts to locate the missing man.

Mark Mardell, North America editor

There is no doubt at all that America's enemies - the people they have fought, and say are finished as a force - are using this swap to proclaim that they are far from beaten.

David Sedney - Deputy Assistant Secretary of Defense for Afghanistan, Pakistan and Central Asia until recently - said: "The video is important in the context of the Taliban hailing the recent exchange as a victory for them.

"They are using it to try to counterbalance the victory the Afghan people won over them in the elections. The massive turnout was roundly trumpeted in the Afghan world as a victory over the Taliban.

"They are now using this exchange as a validation - saying: 'Look how important we are, look how successful we are.'"

Taliban tout prisoner swap 'victory'

On Wednesday, US Secretary of Defense Chuck Hagel said the Army would conduct a "comprehensive review" of the circumstances surrounding his disappearance.

The Mr Hagel said he was unaware of "specific circumstances or details of US soldiers dying as a result of efforts to find and rescue Sgt Bergdahl".

In closing remarks at a Nato summit in Brussels, the US defence chief also said the first priority was to get the soldier - currently in a stable condition in hospital - well and re-unified with his family.

Later a US defense official told the BBC Mr Hagel had called the Bergdahl family and assured them the soldier would continue to receive full support in regard to medical care and reintegration.

Meanwhile, Adm Mike Mullen, who was chairman of the US Joint Chiefs of Staff when Sgt Bergdahl was captured, defended the prisoner swap.

"In every war at some point in time, you do sit down and negotiate," he told the BBC.

"I was encouraged by the fact that at least the Taliban could sit down, conduct a negotiation, and in fact, come to some conclusion. So there may be a possibility to resolve this long term in those kind of negotiations."

Sgt Bergdahl's parents - who have relentlessly campaigned for his release - earlier confirmed they still had not spoken to their son.

His father said he would be flown to an army medical centre in Texas following medical treatment in Germany.