Supporters of Catalan independence responded to new harassment by the Spanish government with a million-strong march on Monday.
The annual demonstration came in the run-up to a referendum planned on 1 October by the Catalan government, but banned by Spain.
Cops raided a print shop and the offices of a Catalan newspaper on Friday, in an investigation the courts said concerned Catalan politicians.
Catalan president Carles Puigemont accused them of “looking for a fight”. He has vowed to declare independence within days if the referendum result is a yes.
Spanish prime minister Mariano Rajoy called the referendum an “intolerable act of disobedience”.