In Barcelona, a huge rally started calling for Spanish unity, a day after Catalonia was stripped of its autonomy.
Many of those protesting in the region's largest city brought signs calling for sacked Catalan leader Carles Puigdemont to be jailed.
Puigdemont was dismissed as Spain's central government took control of Catalan institutions, reports BBC.
On Sunday, a minister in Belgium said he could get political asylum there.
Spain has been gripped by a constitutional crisis since an independence referendum, organised by Carles Puigdemont's separatist government, was held earlier this month in defiance of a ruling by the Constitutional Court which had declared it illegal.
The Catalan government said that of the 43 per cent of potential voters who took part, 90 per cent were in favour of independence.
Friday saw the regional parliament declare independence, with Madrid responding by declaring the move illegal.
Prime Minister Mariano Rajoy then announced the dissolution of the regional parliament and the removal of Puigdemont as Catalan leader, and ordered that fresh regional elections should be held in December.
Puigdemont has urged "democratic opposition" to direct rule from Madrid, which has said it would welcome his participation in the election.
Belgium's migration minister Theo Francken told local TV the separatist leader could be given asylum protection which Spain would find difficult to reverse.
"If you see the situation at the moment, the prison sentences and the repression from Madrid and the prison sentences that are bandied about. Then the question is obviously whether somebody like that has the chance of a fair trial," he said.
There is no suggestion that Puigdemont is seeking to leave Catalonia.
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