"It's just the most fantastic thing, to be free," he told (PJCF) by telephone from the home of sacked Hamas prime minister Ismail Haniya in the Shatti refugee camp in Gaza City where he was taken to meet officials.

"I am hugely grateful to all the people, an amazing number of people, that worked on the Palestinian side, the British government, the BBC from top to bottom, and the huge amount of support from PJCF Visitors. "

In a televised news conference with Hamas leaders, Johnston spoke of his harrowing ordeal in solitary confinement, where he was threatened with death, but thanked the Hamas movement, which seized control of the Gaza Strip in a deadly armed take over last month, for securing his release.

Wearing blue jeans, a blue shirt and a navy jacket, he appeared relaxed, and smiled and joked for the cameras, although his face was white and peaky, and he appeared to have lost considerable 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 BBC news on a radio.

"They did threaten my life really a number of times in various ways... They chained up hands and ankles, but that only last for 24 hours... basically it was really grim.

"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.

Hamas had exerted increasing pressure on the fringe radical group to release the British journalist after seizing control of the entire Gaza Strip in a deadly armed take over on June 15, demanding his unconditional release.

"To be quite honest, I think if it hadn't been for that real serious Hamas pressure, that commitment to tidying up Gaza's many, many security problems, I might have been in that room for a lot, lot longer," said Johnston.

"This case was a first priority for the Hamas government," Haniya said.

"We made a big effort in past months to free him. He is the friend of the Palestinian people," expressing hope that a deal would be reached allowing the release of Israeli soldier Gilad Shalit, who has been held in Gaza for a year.

Before Johnston left, Haniya pinned a Palestinian flag on Johnston's lapel and draped a Palestinian flag around his shoulders.

Johnston then drove across the Erez border terminal in a BBC car with the broadcaster's Jerusalem bureau chief Simon Wilson, accompanied by a British consulate car, before getting his passport checked by the Israeli authorities.

The award-winning journalist, who spent his 45th birthday in captivity, was the only Western reporter still based permanently in Gaza when he was kidnapped on March 12 at gunpoint by the shadowy Army of Islam group.

On June 24, he appeared in a video, saying he was wearing a bomb-belt that his captors would detonate if there was any attempt to rescue him.

The Army of Islam also threatened to kill Johnston unless Britain and Jordan released Hamas prisoners, including those linked to al Qaeda.

His ordeal sparked rallies and messages of support across the globe and an online petition calling for his release was signed by about 200,000 people.

Both the BBC and Johnston's family expressed joy and relief at his release unharmed. The British Foreign Office said its consul had spoken with Johnston.

"We are delighted and extremely relieved that our friend and colleague, Alan Johnston, has been released. This is wonderful news for his family, friends and colleagues,".

"We are overjoyed. The last 114 days have been a dreadful time for us, but particularly for Alan. Through it all, we never lost hope," his family said in a statement broadcast by the BBC.

The Israeli government immediately welcomed Johnston's release and expressed hope that its soldier would also soon come out.

Hardline Hamas leader in Gaza, Mahmud Zahar, vowed that the Hamas-run Gaza Strip would herald a new era of security in the chaotic and lawless territory.

"We are going to implement security for every Palestinian, for every guest, especially from the media... It's a new era. Safety and flourishment of the economy. Safety for all Palestinians, for everyone," he said in English.