Catalan President Carles Puigdemont and other regional leaders have signed a declaration of independence from Spain, following the disputed referendum.
However, they say the move will not be implemented for several weeks to allow talks with the government in Madrid, BBC reported on Tuesday.
The document calls for Catalonia to be recognised as an "independent and sovereign state".
The move was immediately dismissed by the Spanish central government in Madrid.
A October 1 referendum in the north-eastern province -- which Catalan leaders say resulted in a Yes vote for independence - was declared invalid by Spain's Constitutional Court
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Earlier on Tuesday, Puigdemont told the Catalan parliament in Barcelona that the region had won the right to be independent as a result of the vote.
The referendum resulted in almost 90 per cent of voters backing independence, Catalan officials say. But anti-independence voters largely boycotted the ballot - which had a reported turnout of 43 per cent - and there were several reports of irregularities.
National police were involved in violent scenes as they manhandled voters while implementing the legal ruling banning the referendum.
The declaration reads: "We call on all states and international organisations to recognise the Catalan republic as an independent and sovereign state.
Puigdemont told the regional parliament that the "people's will" was to break away from Madrid, but he also said he wanted to "de-escalate" the tension around the issue.
"We are all part of the same community and we need to go forward together. The only way forward is democracy and peace," he told deputies.
But he also said Catalonia was being denied the right to self-determination, and paying too much in taxes to the central government in Madrid.
Spain's Deputy Prime Minister Soraya Saenz de Santamaria responded to Tuesday's developments by saying: "Neither Puigdemont nor anybody else can claim... to impose mediation.
"Any dialogue between democrats has to take place within the law."
She added: "After having come so far, and taken Catalonia to the greatest level of tension in its history, President Puigdemont has now subjected his autonomous region to its greatest level of uncertainty.
"The speech the president... gave today is that of a person who does not know where he is, where he's going, nor who he wants to go there with."
Spanish Prime Minister Mariano Rajoy has called an extraordinary cabinet meeting for Wednesday morning to address the latest moves in the crisis.
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