Lahcen Ikassrien was arrested in June as part of a raid against Islamic radicals. álvaro García / EL PAÍS

Madrid’s largest mosque was functioning as a Jihadist recruitment center led by a former Guantánamo prisoner, it has emerged.

Lahcen Ikassrien, 47, a Moroccan national who was arrested in Afghanistan in 2001 and released after nearly four years in Guantánamo, was using the cafeteria at the Mezquita de la M-30 (named after the adjacent ring road) to recruit and indoctrinate new combatants for the fronts in Iraq and Syria, according to a High Court investigation.

Ikassrien is one of several people who were arrested in June in a raid against an international network that recruited jihadists for the terrorist organization Islamic State in Iraq and Syria (ISIS), which has links to Al Qaeda.

Suspects’ relatives have confirmed that the men became more radical in their beliefs

Investigating judge Pablo Ruz this week prosecuted 15 members of that ring.

Suspects’ relatives have confirmed that the men became more radical in their beliefs after contacting with Salafist activists at the Madrid mosque.

The group called itself the Al-Andalus Brigade after the medieval name for Muslim-controlled parts of Spain and Portugal.

Hicham Chentouf, who joined ISIS in the fall of 2013, began visiting the mosque – whose formal name is the Cultural Islamic Center of Madrid – in 2010. After a year seeing Ikassrien’s people, Hicham grew a beard and embraced the strictest form of Islam. He was appointed imam of the mosque in Yunquera de Henares (Guadalajara), and in 2014 he began publishing pictures of himself brandishing AK-47 rifles on Facebook.

Another member, Ismail Afalah, left his job and joined ISIS in Syria after spending a year with the ring members at the Madrid mosque. His parents thought he was away on vacation.

The ringleader, Lahcen Ikassrien, was acquitted by a Spanish court in 2006 after his release from Guantánamo and sued the state for damages, although his case did not prosper.

The new investigation shows that the ring had a country property near Ávila that was being used to train combatants. The judge describes Ikassrien as “the charismatic leader” of the Salafist group. A search of his Madrid home yielded a wealth of material relating to his recruitment and training activities. He now faces charges of terrorist association and forgery, as he was in possession of a fake residency permit.