Police said the operation on Tuesday was carried out in conjunction with Belgian security forces as part of an eight-month investigation into a group of alleged Islamist militants.

Some of those arrested were being investigated for links to the Brussels suicide bombings in March last year, which killed 32 people at the city's airport and a metro station, a police spokesman said. The terror cell that carried out the Brussels attacks also had links to the November 2015 attack in Paris.

Those detained on Tuesday were all Moroccans aged between 21 and 39 who lived in the Catalonia region. Some were also suspected of links with organized crime in the Barcelona area.

The investigation remained open, police said.

According to the Spanish Interior Ministry, 22 people have been arrested in 16 operations in Spain this year in connection with Islamist extremism. Those figures did not include the arrests made Tuesday.

se/rt (AFP, Reuters, AP)