By Inmaculada Sanz

BARCELONA (Reuters) - Millions of Catalans voted on Sunday in a symbolic referendum on independence from Spain that supporters hope will propel the issue further despite opposition from Madrid.

The "consultation of citizens" in the wealthy northeastern region follows a legal block by the central government against a more formal, albeit still non-binding ballot which regional leaders had been pushing for originally.

Because of the legal restrictions set on it, the ballot was set up and manned by grassroots pro-independence organizations, and Spanish unionist parties argue that, even for that reason alone, it could not legitimately reflect the wishes of anyone.

The restrictions on the vote also means that the turnout number, more than 2 million of 5.4 million potential voters according to the regional government head Artur Mas, will likely be considered more important than the results of the vote itself, expected on Monday.

"We have earned the right to a referendum," Mas told cheering supporters. He qualified the vote as a historic success, setting the stage for a full referendum.

"Once again Catalonia has shown that it wants to rule itself."

Rafael Catala, Spain's Justice Minister, accused Mas of organizing "an act of pure political propaganda with no democratic validity. A sterile and useless event." He said the government might take further legal measures against the vote.

The ballot comes after two years of escalating tension between the central and the regional government. The government argues that Catalonia, which makes up about 16 percent of Spain's population, cannot decide something which affects Spain as a whole on constitutional grounds.

Opinion polls show that as many as 80 percent of Catalans back voting on the issue of Catalonia's status, with about 50 percent in favor of full independence.

"If they don't understand us, they should respect us and each of us go on their separate way," said Angels Costa, a 52-year-old shopkeeper who voted in Barcelona.

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"We would have liked to have been a federal state but that is no longer possible. They've trampled on us too much."

TENSIONS SIMMER

Pro-independence organizations campaigned vigorously for a big turnout from the wealthy region's 7.5 million population, and more than 40,000 volunteers helped set up informal voting stations.

Pro-secession politicians hope a high turnout will prompt central government to sit down with them and negotiate more tax and political autonomy, or even convince Madrid to accept a full-blown independence referendum in the future.

"Banning democracy is always a big mistake," the head of Catalan independence party ERC, Oriol Junqueras told Reuters at a polling station.

ERC is currently ahead in opinion polls in the region.

"We hope this becomes ... the decisive step to obtain a pro-independence majority in the Catalan parliament that allows us to proclaim Catalan independence," he said.

Officials from Catalonia's two main parties, including Mas' centre-right Convergencia i Union (CiU), had suggested that backing from more than 1.5 million citizens would help build momentum for their cause.

The vote has raised hackles in a country in which the memory of Francisco Franco's 1939 to 1975 dictatorship and the suppression of the Catalan and Basque cultures underpins sensitivities.

Those who are not in favor of separation were not expected to have taken part in Sunday's informal poll.

One such was Roberto Ruiz, a 30-year-old out jogging.

"No, I'm not voting. This will not make any difference and I'm against (independence) anyway. I'm Catalan but I'm Spanish too," he said.

A long-standing breakaway movement in Catalonia, which accounts for one-fifth of Spain's economic output and has its own distinct culture and language, grew in strength during the recent years of deep recession.

In early September, buoyed by a Scottish independence campaign which ultimately lost out in a referendum, hundreds of thousands of Catalans dressed in the yellow and red of their regional flag packed the streets of Barcelona, forming a huge "V" to demand the right to vote.

Officially suspended by Spain's Constitutional Court after the Spanish government sought to stop it, Sunday's informal vote nonetheless passed off peacefully.

Analysts say the poll results should be viewed cautiously.

"While we expect the vote to have a symbolic impact (more than one million people will likely participate) it will not carry significant political implications," Antonio Roldan, Europe analyst at the Eurasia Group consultancy said in a note.

(Writing by Sarah White and Elisabeth O'Leary; Editing by Anna Willard and Eric Walsh)