The pro-unity demonstration on Sunday was organized by the Catalan Civil Society group. The same organization was behind a similar mass rally in Barcelona three weeks ago, when police estimated around 350,000 people took to the streets. Organizers then claimed the figure was over 900,000.

The current march aims to defend Spain’s unity and reject “an unprecedented attack in the history of democracy,” the group behind the event claims, as quoted by AP. The crowds have been marching through the city center heading towards one of the major avenues in Barcelona – the Passeig de Gracia.

Many carry Spanish and EU flags, as well as banners calling for “common sense for co-existence.” Leaders of pro-union parties from the ruling conservatives, pro-business liberals, and socialists are attending the rally, according to AP. Madrid’s official representative in Catalonia, and some members of the central government, have also joined the protest.

Earlier this week, Catalonia’s regional parliament declared independence from Madrid following a secret vote. Almost immediately, the Spanish government invoked Constitution Article 155, meaning direct rule over Catalonia, and announced snap elections to be held on December 21.