An investigative judge has jailed seven suspected jihadists in a case involving alleged discussions about targeting a Jewish bookstore in Barcelona.

Judge Santiago Pedraz said in a report Friday that authorities seized a grenade, knives, shotguns, ammunition and chemicals that could be used for bomb-making during searches that followed 11 arrests Wednesday in the northeastern Catalonia region.

He said the suspects had formed a group they called "Islamic Brotherhood for Jihad Predication" that was linked ideologically to the Islamic State group.

Three of those arrested were released and a 17-year-old suspect identified as a Paraguayan living in Spain for eight years was sent to a juvenile detention center.

Besides the bookstore, the judge says members discussed kidnapping a bank branch manager to finance the group.