LONDON (Reuters) - A former Guantanamo inmate who fled to Yemen to help lead an al Qaeda branch after his release says he was motivated by the memory of abuse he says he suffered in U.S. custody, the BBC reported on Wednesday.

Mohammed al-Awfi in an undated file photo. REUTERS/Saudi Press Agency

Concern about Yemen-based al Qaeda in the Arabian Peninsula has risen sharply since it claimed responsibility for a failed plot to blow up a U.S. passenger jet on December 25.

The group has several former Guantanamo detainees in its ranks, which are believed to number about 300.

The former Guantanamo detainee, a Saudi named Mohammed al-Awfi, said he had been tortured while in detention six years ago at the Bagram U.S. military base in Afghanistan before he was sent to Guantanamo, the BBC reported him as saying.

The memory of this abuse doomed efforts by Saudi officials to ensure he did not resume militant activities, he told the BBC in an interview in Saudi Arabia, where he has been in prison following his surrender to Yemeni and Saudi authorities in 2009.

“When I asked al-Awfi why the rehabilitation program had not worked for him, he said it was because the memories of what he had suffered at the hands of Americans were far more powerful than any corrective inducements he had received in the Care program,” BBC journalist Peter Taylor wrote in an online report, referring to a Saudi deradicalization campaign aimed at former Guantanamo detainees.

“Al-Awfi claimed his U.S. interrogators had done terrible things to him. He alleges they sat him on a chair, made a hole in the seat, and then “pulled out the testicles from underneath which they then hit with a metal rod”,” Taylor reported.

“They’d then tie up your penis and make you drink salty water in order to make you urinate without being able to do so, until they make you scream,” Taylor quoted him as saying.

Pentagon officials in Washington had no immediate comment.

Taylor’s interview with Awfi is to be broadcast on Wednesday at 2230 GMT on BBC Television’s Newsnight program.

Al-Awfi and another Saudi freed from Guantanamo, Mohammed al-Shehri, announced in an Internet video in January 2009 that they had joined the Yemen-based al Qaeda group as commanders.

Both men had entered a Saudi rehabilitation program after their release from the U.S. detention center in late 2007.

The program involves counseling by Muslim clerics to alter their thinking, extensive contact with their families, and practical help to reintegrate them into society.

The program is credited with helping erode support for al Qaeda in the kingdom. But the two men’s well-publicized return to al Qaeda embarrassed the Saudi authorities.

The Saudi Interior Ministry has said Awfi gave himself up in 2009 after contacting his family and asking them to get in touch with officials from the rehabilitation program.

U.S. officials said last week a Pentagon assessment showed about one in five inmates freed from Guantanamo had joined or was suspected of joining militant groups like al Qaeda.

Under pressure to increase safeguards, U.S. authorities on January 5 said they had suspended the transfer of more Guantanamo detainees to Yemen, citing deteriorating security in the country.