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LONDON -- An outspoken former Guantanamo Bay detainee was arrested by British police Tuesday on suspicion of Syria-related terrorism offences.

Moazzam Begg, a British father-of-four, is suspected of attending a Syria terrorist training camp and facilitating terrorism overseas, police said.

Begg was arrested in Pakistan in 2002 on suspicion of supporting and recruiting for al-Qaeda, and was taken to Guantanamo Bay the following year. He was released without charge in 2005 and went on to campaign on behalf of those detained without trial.

Former Guantanamo Bay detainee Moazzam Begg speaks during a press conference in Berlin, Germany, on February 12, 2010.SIMON KLINGERT / AFP - Getty Images, file

He filed a lawsuit against the British government over his detention - eventually reaching an out-of-court settlement – and went on to write a book about his experiences: “Enemy Combatant: The Terrifying True Story of a Briton in Guantanamo.”

He has always denied working for al Qaeda, telling NBC News in 2006: “I never fought with al Qaeda or the Taliban or have been a member of either and I think the Americans clearly know this after being held by them and being interrogated over a hundred times.”

However, he recently wrote about his visits to Syria - where the country's civil war has been complicated by the presence of Islamist militant fighters - and had his passport confiscated in December by British authorities.

Begg, 45, was one of four people – three men and a woman – arrested Tuesday in Birmingham, West Midlands Police said in a statement. Three homes were being searched.

British authorities do not normally identify people who have been arrested but not charged.

However, a West Midlands Police spokeswoman told ITV News that it was identifying Begg “as a result of the anticipated high public interest.”

She added that naming Begg does "not imply any guilt".