The Briton, by far the longest-held Westerner in the radicalised and impoverished Gaza Strip, was released to the outside world before daybreak clutched by Hamas officials and surrounded by men waving guns in the air.

"It's just the most fantastic thing, to be free," he told BBC television by telephone from the home of sacked Hamas prime minister Ismail Haniya in the Shatti refugee camp where he was invited for breakfast of hummus and cheese.

Johnston spoke of his harrowing 114-day ordeal in solitary confinement, where he was threatened with death, but thanked Hamas -- which seized control of the Gaza Strip in an armed takeover last month -- for securing his release.

"They talked about killing me and torturing me," he told reporters after crossing into Israel, before driving to the British consulate in Jerusalem. "They handcuffed me and put a hood and took me out in the middle of the night."

Wearing blue jeans, a blue shirt and a navy jacket, he appeared relaxed, and smiled and joked for the cameras, although his face was pale and he had visibly lost weight while being held by the extremist group The Army of Islam.

"The last 16 weeks of course just the very worst you can imagine of my life. It was like being buried alive really, removed from the world and occasionally terrifying," he said, expressing his "unimaginable relief" at being released.

He said his captors threatened his life, held him in solitary confinement and for 24 hours chained his hands and ankles, although he had been bolstered by international support and being able to listen to the BBC World Service.

"There was almost no violence until the last sort of half an hour when they did start to hit me a bit but nothing serious," he said.

"You were in the hands of people who were dangerous and unpredictable. And always frightening in that you didn't know when it might end," he said.

Johnston was released to the commander of Hamas's military wing who drove to a hideout in northern Gaza after the Islamist movement cut a deal with the Army of Islam and a local mufti put out a fatwa for Johnston's release.

Under the deal, Hamas agreed not to press charges against his kidnappers and agreed to release one of its leaders Khattab al-Maqdissi overnight in exchange for the Army of Islam's release of nine Hamas officials, security sources said.