Thousands of right-wing protesters took to the streets of Madrid on Sunday against the Spanish government's plans to pardon 12 Catalan politicians who were convicted over a failed independence attempt in 2017.
The Spanish nationalist Vox party, centrist Ciudadanos and conservative People's Party were among those rallying in Colon Square.
Leader of Vox, Santiago Abascal, said: “The pardons are, first of all, a betrayal to all the Catalans who suffered the separatist coup of 2017 and who were abandoned to the mercy of separatism. It is also an act of betrayal to all the Spanish people who respect law and the constitution."
In 2019 Spain's Supreme Court sentenced nine Catalan separatists on sedition charges for their part in organising an unauthorised referendum on independence.
Three others avoided jail terms.
Prime Minister Pedro Sanchez has not yet issued the pardons but ministers have suggested they are likely to happen.
PM trying to build bridges with Catalans
It is a risky strategy by the PM who wants to build bridges with disenfranchised Catalans but faces the disapproval of more than 60 percent of Spaniards. A mere 25 percent of Spaniards support the move.
Detractors say the separatists have not shown any remorse for their defiance to the Spanish Constitution and that Sanchez is making concessions to them in exchange for support in the national parliament.
Tensions over secession grew in earnest a decade ago amid the economic hardship of the Great Recession and discontent over Spain's opposition to more autonomy for the Catalan-speaking region of 7.5 million people.
The issue has dominated political debate and is thought to have contributed to the rise of the nationalist Vox party.