More than 200,000 people took to the streets in Barcelona, demanding the release of two men they consider political prisoners after they were arrested earlier this week on charges of sedition.
Chanting "Freedom for Sanchez and Cuixart!" protesters called for the release of Jordi Cuixart of Omnium Cultural and Jordi Sanchez of the National Catalan Assembly (ANC) who were imprisoned without bail in Madrid on Monday, pending a trial on charges of sedition in relation to their separatist organising efforts.
The 200k-strong march took place late on Tuesday with the help of Committees for the Defense of the Referendum (CDR), neighbourhood groups created at the beginning of October to "defend the Catalan right to vote," Anna Martinez, one of the CDR organisers, told Al Jazeera.
Martinez is affiliated with a CDR in La Verneda – La Pau, a working-class area in the northwest of Barcelona.
She said she never thought the Spanish government would take political prisoners.
"It's shocking. The situation has become very serious," she said.
Catalans voted to secede from Spain, but turnout was reportedly lower than 50 percent.
On October 10, Catalan president Carles Puigdemont declared an independent Catalan state and then suspended the effects of the declaration. He says his intent was to foster dialogue with Madrid.
Spanish Prime Minister Mariano Rajoy then gave him until Monday morning to clarify whether or not independence was declared., warning that he would enact Article 155.
Referred to as the "nuclear option", Article 155 of the Spanish constitution has never been used before and allows the central government to take control of Catalonia's regional government.
Puigdemont responded Monday with an offer of two months of dialogue, but failed to clarify the stance on independence.
Madrid has extended the ultimatum until Thursday morning. The central government has reiterated its warning that if Puigdemont does not clarify his stance by this deadline, Article 155 will be enacted.