Spanish police arrested three brothers of Pakistani nationality suspected of spreading Islamic extremist propaganda via social media networks.
Officers detained the men, aged between 25 and 31, in an early morning raid on their home in the northeastern city of Lleida, a police spokesman said.
The brothers operated several social media accounts to upload videos praising group executions carried out by Islamic State, the Taliban and other Pakistan-based extremist groups, police said in a statement.
Police said the brothers had attracted a large number of followers in their attempts to spread jihadist ideology.
The raid comes three days after a gun attack by a suicide bomber at Istanbul's Ataturk airport killed 44 people and which Turkish officials said appeared to have been carried out by the Islamic State group.