Hundreds of thousands flooded the streets of Barcelona Sunday to call for Catalonia to remain part of Spain, two days after regional lawmakers exacerbated a political crisis by voting for the wealthy region to secede.

Organizers said the rally's goal was to defend Spain's unity and reject "an unprecedented attack in the history of democracy." Leaders of rival pro-union parties from the ruling conservatives, the pro-business liberals and the socialists joined together under the slogan "We are all Catalonia. Common sense for coexistence!"

Societat Civil Catalana, the pro-union grassroots group who organized the demonstration, said more than 1 million people turned out, while the police put the figure at 300,000.

The mood was festive, with demonstrators waving Spanish, Catalan and European flags and chanting slogans in favour of remaining part of Spain. "We won't let Spain to be torn apart into pieces," read one banner. "The awakening of a silenced nation," read another.

No incidents of violence were reported.

Friday's vote by pro-independence lawmakers in favour of independence, and Madrid's response triggering unprecedented constitutional powers taking control of Catalan affairs, was the climax of Spain's worst political crisis in decades. Spanish Prime Minister Mariano Rajoy has dissolved Catalonia's parliament and called a new regional election for Dec. 21.

"Catalan leaders have broken the law. The central government has let this situation go for too long, for even 30 or 40 years, thinking that we were never going to arrive to this extreme, but here we are," said Angelita Cuesta, a 66-year-old retiree at the rally. "Our society is fractured, there are family members and friends who no longer can talk about politics to avoid conflict."

Three weeks ago, the same group organized another mass rally that brought hundreds of thousands onto Barcelona's streets. That was by far the largest pro-union show of force in Catalonia in recent years, in contrast to huge rallies by separatists.

"We have organized ourselves late, but we are here to show that there is a majority of Catalans that are no longer silent and that no longer want to be silenced," Societat Civil Catalana president Alex Ramos said.

Members of Spain's central government, including Health Minister Dolors Montserrat, and Enric Millo, who is Madrid's representative in Catalonia, also attended the rally. No major pro-independence marches were expected.

Catalonia's separatist leader Carles Puigdemont, who was fired along with his regional government on Saturday, has called for Catalans to engage in peaceful opposition to Spain's takeover of regional affairs.

In a televised message Saturday, he said he and other regional officials fired by Madrid would keep "working to build a free country," in a veiled refusal to accept his Cabinet's dismissal.

The top politicians for pro-union parties wanted to use Sunday's rally as a launch-pad for the critical elections in just over six weeks.

"It's time to take over the streets and take over the ballot boxes," said Albert Rivera, the leader of the centre-right Citizens party.

Separatists won 48 per cent of the vote in Catalonia in the 2015 regional election, although they took more seats in the regional parliament because of Spanish election law which gives more weight to sparsely populated areas.

Oriol Junqueras, the ousted vice-president of Catalonia's rebellious government, wrote in an open letter in Catalan newspaper El Punt-Avui on Sunday that separatists should consider participating in the elections. Some secessionists have argued for a boycott.

The Catalan parliament's vote to secede came after an Oct. 1 referendum in favour of independence deemed illegal by Spain's constitutional court. Opponents to secession boycotted the vote after separatists violated parliament rules to push through its convocation.

Voting on the day itself was marred by violence when national police clashed with people attempting to cast their ballots, in what was widely seen in the region as a heavy-handed response by Spanish police. Spain's government said the police response was proportionate.

There are fears the political turmoil could also have a severe economic impact on the region.

Addressing the crowd at Sunday's rally, Josep Borrell, former European Parliament president and a Spanish ex-minister, said the central government's move to take control of some regional affairs under the Constitution's Article 155 was the only thing preventing a full-blown economic crisis in Catalonia.

If the government had not triggered the constitutional powers, "many of you would have lost your jobs . and if that hasn't happened it's because thanks to the application of Article 155 businesses and markets understand that there won't be (secession)," he said.

If Spain had not taken over, even more business would have left Catalonia in recent weeks that the 1,700 companies which relocated headquarters to other parts of Spain recent weeks, he said.

Spain's government has said the ousted Catalan leaders could be charged with usurping others' functions if they refuse to comply with their firing. On Sunday, a Belgian government official said it would be "not unrealistic" for Puigdemont to ask for asylum, and warned it would create serious diplomatic difficulties with fellow European Union member state Spain.

Asylum State Secretary Theo Francken said on Twitter that "it is possible to ask for asylum as an EU subject" in Belgium, adding it was up to independent asylum authorities whether to grant it.

The 28-nation EU is considered a bloc where the rule of law applies and granting asylum based on arguments that repression would endanger the full exercise of one's rights would be exceptional.

"If you assess the situation at this stage, including the prison terms and the repression from Madrid," Francken told VTM network, "there is the question whether a person like that can get a fair trial, of course."

In another tweet, he stressed Belgium wasn't seeking such a scenario. "I am not rolling out the welcome mat," he said.

In the past, some Basque separatists have asked for asylum in Belgium and weren't extradited to Spain, causing years of friction.