Updated

A former Guantanamo Bay detainee who is a well-known advocate for the rights of terrorism suspects was arrested on suspicion of Syria-related terrorism offenses, British police said Tuesday.

West Midlands Police said Moazzam Begg was one of four people arrested in the Birmingham area of central England.

Police said Begg, 45, is suspected of attending a terrorist training camp and facilitating terrorism overseas.

He was arrested along with a 44-year-old woman, her 20-year-old son, and a 36-year-old man, who are all suspected of facilitating terrorism overseas. Their names were not released.

Police in Britain do not usually name suspects until they are charged. The force said it was identifying Begg to the media "as a result of the anticipated high public interest."

The four suspects were being questioned at a Birmingham police station, while counterterrorism officers searched their homes.

In 2002, Begg was arrested in Pakistan as an "enemy combatant." He was detained by U.S. forces at Bagram in Afghanistan and later sent to the prison camp in Cuba.

After his release without charge in 2005 he became a director of the advocacy group Cage, which campaigns against alleged abuses committed in the name of fighting terrorism. He is a well-known figure who appears frequently in British media.

Cage said it was outraged by Begg's arrest and accused the government of trying "to ensure that any travel to Syria is deemed suspicious."

"We ... see his arrest as politically motivated and as part of a campaign to criminalize legitimate activism," said the group's research director, Asim Qureshi.

British intelligence officials say hundreds of Britons are estimated to have traveled to Syria to join the battle against the forces of President Bashar Assad. Governments in Britain and other European countries have expressed concern about the potential domestic threat posed by battle-hardened fighters returning from Syria after joining al-Qaida-affiliated groups.

British police have stepped up the number of arrests made over suspected Syria-related terrorism.

In December, Begg said authorities had revoked his British passport after he visited Syria. He wrote on the Cage website that his trips there, in 2012, had been approved by MI5, Britain's domestic intelligence service.