Violence erupted at a campaign against Catalonian independence as protesters appearing to give Nazi salutes clashed with police in Barcelona.
The rally came as the deposed president of Catalonia Carles Puigdemont faced charges that could see him jailed for up to 30 years.
Footage showed parts of the march, attended by hundreds-of-thousands of protesters, descend into chaos on Sunday evening as demonstrators clashed with armed officers.
Tensions rose as police in riot gear swiped at angry protesters draped in the Spanish flag, campaigning for Catalonia to remain part of Spain.
The footage showed a participant giving what appeared to be a Nazi salute.
At a pro-unity protest in Madrid two days earlier, some participants had also been seen giving far-right Nazi salutes.
Prosecutors are expected to file rebellion charges later today against deposed president Puigdemont who was sacked on Friday after Spanish PM Mariano Rajoy invoked a never-before-used article in the constitution to seize back control of the region.
Rebellion carries a sentence of up to 30 years in prison.
The country has been plunged into a constitutional crisis after the Catalan Parliament declared itself independent in a vote on Friday.
By Saturday, Madrid had sacked Puigdemont, stripped top police officials of their powers and called a snap election for Catalonia’s parliament as it imposed direct rule.
After pro-independence celebrations on Friday, a mass pro-unity rally flooded the streets of Barcelona on Sunday.
Most were peacefully demonstrating for a unified Spain.
Organisers said the goal of the rally, which joined leaders of different pro-union parties, was to reject "an unprecedented attack in the history of democracy."
The protest’s slogan read: "We are all Catalonia. Common sense for coexistence!"
