(Updates with Taliban comments, paragraphs 1-5, 8)
By Katharine Houreld
ISLAMABAD July 10 (Reuters) - U.S. soldier Bowe Bergdahl, who was held captive by the Taliban for five years, appeared smiling alongside a commander from the militant Haqqani network in a photo posted on a Twitter account by a supporter of the Afghan Taliban.
On Friday, the Taliban confirmed the photo had been taken with them while Bergdahl was in captivity.
"You would have noticed in the photo with Badruddin Haqqani, Bergdahl is looking physically very weak as it was the beginning when he was kidnapped by our lions," said a Taliban commander, who asked not to be named.
Taliban spokesman Zabihullah Mujahid said the account that posted the photo was operated by a Taliban sympathiser who works in a university in Afghanistan.
"Its not our official Twitter but is operated by someone who seemed to be our supporter and sympathiser. We know he is teaching in a university in Afghanistan and is often using our photos on his Twitter," Mujahid said by telephone.
The account posted the photo late on Wednesday along with others of Bergdahl, as well as gruesome images of a decapitation. It said Bergdahl had been treated with kindness in captivity.
"Bowe #Bergdahl was really impressed when he saw the hospitality of #Taliban He first thought that he will be tortured But he was wrong," the Twitter post said. "He was not shackled in Chains neither was he Tortured, Rather He was Free."
Another photo of him with a Taliban commander showed him looking haggard and worried. The account also said Bergdahl had attempted to escape when the Taliban took him to a market but had been recaptured.
Bergdahl was captured on June 30, 2009, in unclear circumstances. He was released on May 31 in a prisoner swap that freed five Taliban leaders held at Guantanamo prison in Cuba.
He has not spoken to the media since his release and the Twitter account's description of his time in captivity and the circumstances of the photographs could not be confirmed.
The Twitter account identified the man in the first photo with Bergdahl as Badruddin Haqqani, head of operations and financial chief for the Haqqani network. The group is blamed for some of the deadliest and most spectacular attacks on NATO and Afghan troops in Afghanistan.
The picture with Haqqani is tagged with the words "Jundul Haqqani", or Haqqani group.
A drone strike killed Badruddin Haqqani in northwestern Pakistan in 2012.
Bergdahl's release sparked an initial wave of euphoria in the United States that quickly became overwhelmed by a bitter political debate over whether he had abandoned his post and whether the prisoner swap should have gone ahead.
Some of his former colleagues have called for him to be court-martialed for allegedly deserting his post.
U.S. Defense Secretary Chuck Hagel said the army was investigating the circumstances of Bergdahl's disappearance. He was the only U.S. soldier to be captured and held hostage during the war in Afghanistan.
Bergdahl was initially flown to a U.S. hospital in Germany. He arrived back on U.S. soil last month and has been housed at a military hospital in San Antonio, Texas, to help him readjust.
The hospital, formally known as the San Antonio Military Medical Center, has teams of specialists and has been helping returning prisoners of war for decades. (Reporting by Katharine Houreld; Editing by Gareth Jones and Paul Tait)