Hundreds of thousands are attending a rally for Spanish unity in Barcelona after Catalonia was stripped of its autonomy for declaring independence.
Many of those protesting in the region's largest city chanted that sacked Catalan leader Carles Puigdemont should be jailed.
Mr Puigdemont was dismissed as Spain's central government took control of Catalan institutions.
On Sunday, a minister in Belgium said he could get political asylum there.
Spain has been gripped by a constitutional crisis since a referendum, organised by Mr Puigdemont's separatist government, was held earlier this month in defiance of a ruling by the Constitutional Court which had declared it illegal.