Spain is poised to begin voting in regional elections as thousands of young protesters remain camped out in squares across the country.
Demonstrators are angry at the government’s economic policies and Spain’s high youth unemployment rate.
Their numbers have swelled despite a ban on political protests ahead of elections.
The governing Socialists are expected to suffer major losses in voting for city councils and regional governments.
Prime Minister Jose Luis Rodriguez Zapatero’s government is struggling to overcome recession and create jobs.
In the capital Madrid, about 30,000 people have occupied the central Puerta del Sol square.
Similar protests, popularly known as M-15, have sprung up in many other cities including Barcelona, Valencia, Seville and Bilbao.
The crowds camped out in Madrid and across Spain say they are not demonstrating against this government but against a whole political class.
They are frustrated by mass unemployment, angry at the financial markets’ influence on policy and fed up at with wide-scale corruption.
The protest camp is a cry for change, an outpouring of indignation.
This high-profile protest is very uncomfortable for the Socialist government. It was already predicted to fare badly at the polls for allegedly failing to protect Spain from the economic crisis.
Now it is possible many will decide not to bother voting at all or spoil their ballot papers.
“I’m happy that they’re finally protesting. It was about time,” said Maria, an elderly woman visiting her grandson in the Puerta del Sol.
Protest organisers have urged those taking part not to confront the police, and have tried to discourage the distribution of alcohol.
“It’s a revolution, not a drinking party,” read one sign.
Brooms donated by supporters are being used to keep the square clean, witnesses say.
The BBC’s Sarah Rainsford in Madrid says there is also a creche, a kitchen area and even a vegetable patch.
One protester, Alejandro, said: “I hope this changes our situation. We have a right to regular jobs, a future and a decent salary, to more opportunities in life, the chance to get a house, to pay for that house without being enslaved, but especially a better quality of life.”
The protesters are urging people not to vote for either of Spain’s two main parties – the governing Socialists or the centre-right opposition.
Analysts say that despite the strength of the protests, they are unlikely to affect the outcome of Sunday’s elections, other than to worsen the Socialists’ defeat.
The Socialists are predicted to lose control of strongholds such as Barcelona, Seville and the Castilla-La Mancha region.
Spanish law forbids political rallies on the day before elections to allow for a “day of reflection”.
But as the ban came into effect, the crowds stayed put and police did not try to disperse them.
Organisers say the protests may continue after the elections.
The demonstrations began six days ago in Madrid as a spontaneous sit-in by young people frustrated at 45% youth unemployment.
Spain’s overall jobless rate soared to 21% in the first quarter of this year, the highest in the industrialised world.
Dubbed “los indignados” [the indignant], the protesters are demanding jobs, better living standards, a fairer system of democracy and changes to the government’s austerity plans.
Prime Minister Zapatero had urged protesters to respect the day of reflection but also said he was sensitive to their concerns and praised their “peaceful manner”.
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