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Spanish authorities have shut down a suspected Islamic State (ISIS) terror cell on the resort island of Mallorca in a series of raids across Europe, CNN reported on Wednesday.

A coordinated anti-terror operation saw officials swoop in to arrest six people for allegedly raising funds and recruiting fighters for ISIS, authorities in Spain, the United Kingdom and Germany said in statements on Wednesday.

According to Spanish authorities cited by CNN, four of the six were detained in Mallorca, while the others were taken into custody in the UK and Germany.

Spanish National Police said the investigation linking the group to ISIS started in 2015 when a website with several terrorist propaganda videos was discovered.

During the course of the two-year probe, according to the report, authorities identified a UK-based Salafist imam who was allegedly orchestrating the production of online extremist propaganda.

The 44-year-old imam, whose identity has not been publicly disclosed because of ongoing proceedings, was detained on terrorist offenses at an address in Sparkhill, Birmingham, by the West Midlands Counter Terrorism Unit at the request of Spanish authorities.

According to Spanish police, the man is believed to be the group's spiritual leader and is known to have traveled to Mallorca on multiple occasions to set up the group that included the four who were arrested in Spain on Wednesday.

The imam's public speeches had already put him on the radar of British and European security services, the police said.

The man taken into custody in Germany is also believed to have been working with the group and had taken part in several of their propaganda videos, according to the Spanish National Police.

Authorities took action across Europe on Wednesday after the investigation appeared to indicate that the group's following was growing as a result of increased social media activity and secret weekly meetings at which their extremist ideology was being disseminated.

Europe has been under a terror threat in recent years, and ISIS terrorists have been able to carry out attacks in the continent.

Among the more recent terrorist attacks was a combined attack on the London Bridge and a nearby market.

Last week, a suspected ISIS sympathizer set off a bomb at a Brussels train station.

Spain itself heightened its anti-terror alert to level four of a possible five in June of 2015.

That year, the country arrested a Spaniard in the Spanish north African territory of Ceuta on suspicion of recruiting youth to fight for the ISIS in Syria.

Also that year, two men and a woman suspected of belonging to a cell that recruited women online to join ISIS were detained in Spain.