Catalan leader Carles Puigdemont and other regional leaders have signed a declaration of independence from Spain.
However, they say secession will be suspended to allow talks with the government in Madrid.
It is unclear whether the document – calling for Catalonia to be recognised as an “independent and sovereign state” – has any legal status.
The move was immediately dismissed by the Spanish central government in Madrid.
A 1 October 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.
Earlier on Tuesday, Mr Puigdemont told the Catalan parliament in Barcelona that the region had won the right to be independent as a result of the referendum.
The referendum vote resulted in almost 90% of voters backing independence, Catalan officials say. But anti-independence voters largely boycotted the ballot – which had a reported turnout of 43% – 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.
“We call on the Catalan government to take all necessary measures to make possible and fully effective this declaration of independence and the measures contained in the transition law that founds the republic.”
Mr 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.
He hailed the referendum process and condemned the actions of the Spanish government, but acknowledged that people on all sides were worried about what would happen next.
“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 Mr Puigdemont nor anybody else can claim… to impose mediation.
“Any dialogue between democrats has to take place within the law.”
‘Threat still on the table’
By the BBC’s Tom Burridge, in Barcelona
The incredible game of cat and mouse between the Madrid government and the Catalan devolved government continues.
And that’s been the tactic all along from the Catalan government. It’s been putting threats on the table, it’s been speaking to the media and saying: “We will go ahead and declare independence from Spain come what may”; “We will hold that referendum even though it has been declared illegal by the Spanish state, even though they try to arrest officials and try to break it up”.
And now Carles Puigdemont is saying: “I am still going to declare independence from Spain, but I am giving them some time, a window.”
That is a window where there can in theory be mediation – and we are hearing that there are mediation efforts by an international organisation, according to our sources, involving very very senior international political figures.
In a sense his stark warnings haven’t changed. But he will still be under pressure, not only from his own party but other pro-independence Catalan parties which he depends on for a majority in parliament to actually keep this whole project going.
He’s given them maybe enough, but is their patience going to run out? And then there’s the other dimension in this – the Spanish government in Madrid.
Independence supporters had been sharing the Catalan hashtag #10ODeclaració (10 October Declaration) on Twitter, amid expectations that Mr Puigdemont would ask parliament to declare independence on the basis of the referendum law it passed last month.
But influential figures including Barcelona’s mayor Ada Colau and European Council President Donald Tusk had urged Mr Puigdemont to step back from declaring independence.
Catalonia, a part of the Spanish state for centuries but with its own distinct language and culture, enjoys broad autonomy under the Spanish constitution.
However, a 2005 amendment redefining the region as a “nation”, boosting the status of the Catalan language and increasing local control over taxes and the judiciary, was reversed by the Constitutional Court in 2010.
The economic crisis further fuelled discontent and pro-independence parties took power in the region in the 2015 elections.
Catalonia is is one of Spain’s wealthiest regions, accounting for a quarter of the country’s exports. But a stream of companies have announced plans to move their head offices out of Catalonia in response to the crisis.
The European Union has made clear that should Catalonia split from Spain, the region would cease to be part of the EU.
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