Qatar has moved five Afghan Taliban prisoners freed in exchange for a US soldier to a residential compound and will let them move freely in the country.

US officials have referred to the release of the Islamist militants as a transfer and said they would be subject to certain restrictions in Qatar.

One of the officials said that would include a minimum one-year ban on them travelling outside of Qatar as well as monitoring of their activities.

"All five men received medical checks and they now live with their families in an accommodation facility in Doha," the Gulf source, who declined to be identified, said.

"They can move around freely within the country."

Following the deal, concerns were expressed by some US intelligence officials and congressional advisers over the role of the Gulf Arab state as a bridge between Washington and the world of Islam.

The Gulf official said the Taliban men, who have been granted Qatari residency permits, will not be treated like prisoners while in Doha and no US officials will be involved in monitoring their movement.

"Under the deal they have to stay in Qatar for a year and then they will be allowed to travel outside the country... They can go back to Afghanistan if they want to," the official said.

The five, who had been held at Guantanamo Bay since 2002, arrived in Qatar on Sunday where US security personnel handed them over to Qatari authorities in the Al Udeid area west of Doha, site of a US military base.

US Army Sergeant Bowe Bergdahl had been held for nearly five years by Taliban insurgents in Afghanistan and his release followed years of on-off negotiations.

A diplomatic source said Qatar has flown in family members of the five released Taliban men and gave them accommodation paid for by the government.

On Sunday, Qatari Foreign Minister Khaled al-Attiyah told a news conference that Doha got involved in the case because it was a "humanitarian cause". He did not elaborate.

Obama defends prisoner swap

US President Barack Obama defended the prisoner swap, saying his "sacred" trust as commander-in-chief outweighed claims he broke the law and set a dangerous precedent.

Mr Obama is facing rising questions about the deal to secure the release of Sgt Bergdahl .

At a press conference in Poland, Mr Obama was unrepentant, as the White House issued a new legal justification for his action.

"The United States has always had a pretty sacred rule. That is we don't leave our men or women in uniform behind," Mr Obama said.

"We saw an opportunity, we were concerned about Sergeant Bergdahl's health ... and we seized that opportunity," Mr Obama said.

Initial euphoria in Washington about Sgt Bergdahl's release has degenerated into a mounting political row, shaped by consistent Republican claims that Mr Obama is a naive leader and a liability as commander-in-chief.

It has also revived a showdown over Mr Obama's still unfulfilled vow to close down Guantanamo Bay - which has repeatedly been blocked by Congress.

The president's decision to sign off on the swap has also been criticised because of reports that Sgt Bergdahl deserted his post in Afghanistan nearly five years ago.

Mr Obama said Sgt Bergdahl's state of health had not yet permitted an interrogation about his capture, but said the mystery of his disappearance did not change his own basic obligation as commander-in-chief.

"We still get an American soldier back if he is held in captivity. Period. Full stop. We don't condition that."

Lawmakers have complained that they were not given the 30 days' notice required by law ahead of prisoners being transferred out of the war on terror camp at Guantanamo Bay, Cuba.

"The process was truncated because we wanted to make sure that we did not miss that window," Mr Obama said.

But he added that his administration had been talking with Congress "for quite some time" about the idea that a prisoner swap may be required to win Sgt Bergdahl's release.