Hundreds of thousands of protesters have taken to the streets of Barcelona after Spain's central government announced it is set to take some powers away from Catalonia's administration.
Barcelona police said 450,000 people had joined a protest in the regional capital, many of them chanting the words "freedom" and "independence" and waving Catalonia's yellow, red and blue separatist flag.
Large crowds have gathered outside Barcelona's Paseo de Gracia boulevard where Catalan leader Carles Puigdemont is due to give his reaction to Madrid's decision.
In an unprecedented move aimed at thwarting secession attempts, Spain's Prime Minister says he has approved implementing the previously unused Article 155 of the country's constitution to assume control of the region.
Mariano Rajoy said he wants the senate to give him permission to dissolve the regional government in Barcelona and call early elections.
He announced the measures to take over the regional cabinet's functions after a crisis meeting of his own cabinet in the wake of the 1 October independence referendum deemed illegal by Madrid.
Under his plans, the powers of Catalan officials would be transferred to the Spanish government - but he stressed he did not want to use them to rule Catalonia directly.
About 90% of Catalans who voted in the referendum backed breaking away from Spain, but only 40% of eligible voters cast a ballot, with many pro-union supporters declining to vote.
The PM's move, aimed at blocking the independence movement, has sparked anger among separatists.
Mr Puigdemont, who has refused to abandon his threat to declare a breakaway state following the controversial vote, is set to join a protest and then give his response.
Carme Forcade, the speaker of the Catalan parliament said the move by Madrid was a "coup and an "attack on democracy".
She went on: "Prime Minister Rajoy wants the parliament of Catalonia to stop being a democratic parliament, and we will not allow this to happen.
"This is why we want to send to the citizens of this country a message of firmness and hope. We commit today, after the most serious attack against the Catalan institutions since they were restored, to the defence of the sovereignty of the parliament of Catalonia."
On the streets of Barcelona, people banged pots and pans and drivers beeped their horns.
Catalonia's administration currently runs its own policing, education and healthcare.
Mr Rajoy said he was concerned about the financial impact if Catalonia broke away, and claimed the latest figures on the economy were "worrying".
A number of companies have already announced plans to move some or all of their operations out of the northeast region.
Article 155 allows central authorities to intervene when one of Spain's 17 autonomous regions fails to comply with the law.
Autonomy is a hugely sensitive issue in Catalonia, which saw its powers taken away under Spain's military dictatorship.
Home to 7.5 million people, the region fiercely defends its own language and culture.
:: What invoking Article 155 means for Catalonia
Meanwhile, King Felipe has said Catalonia "is and will remain an essential part of 21st century Spain".
In an unusually emotional speech at a prize-giving ceremony, he said the Spanish government would resolve the fight over Catalonia's bid for independence through "legitimate democratic institutions".