Spain's Interior Ministry said the four Spanish nationals and one Moroccan citizen set up a cell with a "perfectly organized structure" to follow the directives of Middle East-based terror group "Islamic State" (IS).

One suspect was detained in the western German city of Wuppertal, another in Brussels, and three were taken into custody in Spain - two of them in Barcelona and one in Spain's North African enclave of Melilla, the ministry said in a statement.

They allegedly used a number of social media sites, including a Facebook page "Islam en Español" (Islam in Spanish), to glorify IS and spread the militant group's message. The ministry said the page had 32,500 followers.

The five, who operated almost exclusively in Spanish, are also accused of recruiting militants for IS in Europe, commissioning terror attacks, and promoting Islamic militancy. The ministry added that the cell represented "a serious, concrete and ongoing threat to security in Europe."

Last year, Spain raised its alert level to 4 - its second highest rank for threats. Since then, Spanish police have arrested 143 Islamist militants both inside and outside the country, according to government figures.

In Wednesday's operation, Spanish police worked in conjunction with Belgian Federal Police and Germany's Office of Criminal Investigation.

nm/kl (Reuters, AP, EFE)