Catalan leader Carles Puigdemont has said Spanish Prime Minister Mariano Rajoy's attempt to "humiliate" Catalonia is an "attack on democracy".
He made a veiled independence threat, telling politicians to counter Spain's planned takeover.
Mr Puigdemont spoke out after Mr Rajoy said he wants the country's senate to give him direct power to dissolve the regional Catalan government and call an election as soon as possible.
Mr Rajoy said after a cabinet meeting that the central government needs to take the unprecedented step of assuming control of Catalonia to "restore order" in the face of a secession effort backed by the regional government.
He is proposing that the powers of Catalan officials be taken over by central government ministers.
Mr Rajoy's government is activating a previously untapped constitutional article to take control of Catalonia.
The move is aimed at blocking the independence movement that has gained pace since a disputed October 1 referendum on separating Catalonia from Spain.
Mr Puigdemont wants the regional parliament to debate and vote on how to respond to what he called the Spanish government's "attempt to wipe out" Catalonia's autonomy.
In a televised address late on Saturday, he called plans by Mr Rajoy to replace him and his cabinet an "attempt to humiliate" Catalonia and an "attack on democracy".
His comments were a veiled threat to push ahead with an independence declaration for the prosperous region in north-eastern Spain.
They came after he joined a large protest in Barcelona on Saturday where many were aghast at the plans announced earlier in the day by Mr Rajoy.
Mr Puigdemont called Mr Rajoy's move the "the worst attack" on Catalan people and institutions since General Francisco Franco abolished Catalonia's regional government in 1939.
Even moderate Catalans were aghast at the scope of the move, greeting Mr Rajoy's announcement with banging pots and honking cars in the streets of Barcelona.
Barcelona mayor Ada Colau, who opposes independence without a valid referendum, called Mr Rajoy's measures "a serious attack" on self-government in Catalonia.
Others went further, with Catalan parliament speaker Carme Forcadell accusing Spain's central authorities of carrying out a coup.
"Mariano Rajoy has announced a de facto coup d'etat with the goal of ousting a democratically elected government," he said, calling it "an authoritarian blow within a member of the European Union".