Eight Spaniards have been arrested, accused of fighting alongside pro-Russian rebels in eastern Ukraine.
Police carried out raids in six regions across Spain, according to the interior ministry.
They face charges of complicity in murder, possession of weapons and violating Spain’s neutrality in the conflict.
The eight Spanish fighters were arrested after returning from Ukraine where they apparently took part in the conflict in the Donbas region last year.
A small number of foreign nationals have been fighting on both sides of the conflict, according to the ministry, mainly from Spain, France, Germany, Italy, Poland and Sweden.