Spanish Prime Minister Mariano Rajoy has called for talks with the newly-elected separatists in Catalonia, but said that the "end of unity of Spain" is not for discussion.
On Monday, Rajoy said he was ready to "open a dialogue" with Catalan President Artur Mas and his pro-independence allies, who won Catalonia's election a day earlier.
"There are many things that can be discussed. But while I am the head of the government, I will not discuss the unity of Spain, the national sovereignty or the freedom of all Spaniards," Rajoy told journalists at a press conference on Monday.
The "Together for Yes" group of secessionists won 62 seats in the 135-member parliament, while the left-wing pro-independence Popular Unity Candidacy (CUP) won 10 seats.
“Dialogue is healthy and democratic. What is insane and anti-democratic is to try and break the law,” said Rajoy, ostensibly referring to the Spanish constitution's prohibition on measures toward regional independence.
Ahead of the the elections, Together for Yes leaders promised to implement a "roadmap" designed to result in an independent Catalan state within 18 months.
Sunday's victory provided the pro-independence movement with "enormous strength to push this project forward", said Mas.
Opponents of Catalan independence claim that pro-independence parties won some 48 percent of the vote, just short of the 50 percent they would need to move forward in a real referendum.
But pro-independence leaders say the will move forward with or without the Madrid's participation.
"If the state shows no will to negotiate, we will do it anyway, because we have a mandate," Together for Yes leader Raul Romeva told AFP.
The result would likely provide a boost to separatist movements across Europe and it was met with concern in Spain's powerful neighbour France, which along with Germany, Britain and the United States had urged Spain to stay united.
French Prime Minister Manuel Valls, who was born in Barcelona and became a French citizen after moving to France as a teenager, called on Monday for Spain to remain "united and strong".
"The splitting, division, disintegration of nation states will bring nothing good either to Spain or Europe, and it is up to the Spanish to make the choice," he said.
The nationalist leader of Scotland, where a referendum last year resulted in a "no" to independence, congratulated the Catalan separatists on the result.
"Many people in Scotland, given our recent experience of a referendum, will be looking with great interest at what is happening in Catalonia," the country's First Minister Nicola Sturgeon said in televised comments.
"But we are two different countries with different circumstances... The future of Catalonia will be decided by the people of Catalonia."
The separatist alliance now faces tough negotiations to strike an accord with CUP, an anti-capitalist citizens' group that does not want Mas to lead the separatist movement.
CUP said Monday it was launching meetings with various groups in the new parliament to negotiate a deal.
CUP said it would insist on urgent social aid measures for the poor and that the coalition select a leader other than Mas, who is widely despised on the left.
"We are going to appoint someone who has nothing to do with spending cuts, privatisations and corruption," said CUP's number two candidate Anna Gabriel Sabate.