MADRID (REUTERS) - Spanish police in the northeastern city of Barcelona have arrested eight people and raided 12 properties in a sweeping operation against Muslim militants, police said on Tuesday (April 25).

The detained were all Moroccans aged between 21 and 39, the police said.

The investigation and operation were carried out in conjunction with Belgian police, they said in a statement. A police spokesman declined to say what connection the arrested had with Belgium.

The raids follow an eight-month investigation in which the police observed a group which they said was associated with Islamist militants and had links to organised crime in the Barcelona area.

Spain has arrested some 22 people in 16 separate operations this year in connection with Muslim extremism, according to Interior Ministry figures.