Tens of thousands gathered in Madrid for a protest by right-wing parties opposed to a Spanish government plan to ease tension in the Catalonia region.
The centre-right Popular Party (PP) and Ciudadanos (Citizens) say Prime Minister Pedro Sánchez's plan to appoint an intermediary for talks with separatists amounts to treason.
The separatists have rejected the offer - they want a new independence vote.
Like the right, the ruling Socialists also oppose Catalan independence.
Far-right groups including the Vox party are also present at the protest, held under the slogan "For a united Spain. Elections now!"
Protesters filled the Spanish capital's Colon Square and nearby streets, many of them chanting "long live Spain". Police put the total number of demonstrators at 45,000.