The US military has transported out of Syria an American who disappeared seven months ago into former president Bashar Assad’s notorious prison system and was among the thousands released this week by rebels, an official has said.

Travis Timmerman was flown out of Syria on a US military helicopter, according to a US official who spoke on condition of anonymity to discuss an ongoing operation.

Mr Timmerman, 29, told The Associated Press he had gone to Syria on a Christian pilgrimage and was not ill-treated while in Palestine Branch, a notorious detention facility operated by Syrian intelligence.

He said he was freed by “the liberators who came into the prison and knocked the door down (of his cell) with a hammer”.

Mr Timmerman said he was released Monday morning alongside a young Syrian man and 70 female prisoners, some of whom had their children with them.

He had been held separately from Syrian and other Arab prisoners and said he did not know of any other Americans held in the facility.