Spanish police arrested eight people in pre-dawn raids in Madrid on Monday, against a jihadist recruitment network led by a former Guantanamo Bay inmate, the government said.

Police have so far launched 12 raids in the Spanish capital, detaining eight people, and the investigation remains open, Spain’s interior ministry said in a statement.

The Islamic cell found and despatched recruits for Islamic State of Iraq and the Levant (ISIL) militants based in Syria and Iraq, the ministry said.

ISIL fighters made rapid military gains in Iraq last week, seizing the second-biggest city Mosul and coming within 80 kilometres (50 miles) of Baghdad. Online photos, which cannot be independently confirmed, apparently show ISIL militants massacring captured Iraqi soldiers during the offensive.

“It should be highlighted that the leader of this cell lived in Spain after passing through the Guantanamo military base, having been arrested in Afghanistan in 2001,” the Spanish ministry said, without elaborating.

Spain’s press said the arrested ringleader was Lahcen Ikassriem, a Moroccan who was held for three years in the US prison camp at Guantanamo Bay.

The suspect was reportedly extradited in 2005 to Spain where he was held in preventative detention for more than a year before being freed by the Spanish courts in 2006. The interior ministry was not immediately available to confirm these details.

– Threat of attacks –

President Barack Obama’s administration is trying to shut down the notorious prison at a US military base in Guantanamo Bay, Cuba, where many detainees are suspected of having terrorist links but the authorities often lack sufficient evidence to try them in court.

The Spanish government has said it fears battle-hardened Islamist fighters may return to Spain from Syria and other conflict zones under the influence of Al-Qaeda-inspired groups, posing a threat of attacks.

The latest operation by Spanish security forces is the third significant raid on jihadist recruitment cells announced in Spain in as many months.

On May 30, security forces arrested six suspects in Melilla, one of two Spanish-governed cities along with Ceuta on the northern Morocco coast.

Spain accused the network of recruiting and sending out jihadists to join “terrorist organisations” based in Mali and Libya.

On March 14, Spanish and Moroccan forces arrested seven suspects as they broke up a cell suspected of sending volunteer fighters to Mali, Syria and Libya.

The authorities detained three people in Morocco and another four in Spain — one of whom was caught in the southern city of Malaga and the other three in Melilla.

Spain this year marked the 10th anniversary of the March 11, 2004, Al-Qaeda-inspired bombing of four packed commuter trains in Madrid, which killed 191 people.

Since the Madrid train bombings, more than 470 suspected Islamic extremists have been arrested in Spain, according to the Spanish interior ministry.