Police in Spain say they’ve arrested eight people for allegedly recruiting for the Islamic State in Iraq and Syria (ISIS) – the hardline Islamist terrorist group that has captured large swaths of territory in those countries and is threatening Baghdad itself.

Local media reports say the Spanish group’s leader is Lahcen Ikasrrien – a Moroccan who was arrested on the battlefield in Afghanistan a decade ago and jailed at Guantanamo Bay before being released to Spain in 2005 for lack of evidence.  One of the other seven is reportedly from Spain, another from Argentina, and the rest are from Morocco.

Across Europe, authorities are concerned about the explosive growth of ISIS.  Over the weekend, a French national was arrested by German authorities for alleged recruiting; Belgium wants France to extradite a suspect in last month’s shooting at the Jewish Museum, a militant who spent a year fighting alongside insurgents in Syria; And Dutch authorities say many Islamists from the Netherland had joined ISIS.