The protest, filled with chants, drum beats and whistles, was noisy but peaceful, The Wall Street Journal said. Many carried signs calling for Prime Minister Mariano Rajoy to resign amid media reports charging members of his government have accepted cash kickbacks from businesses seeking state contracts. Rajoy has denied the charges but is under official investigation.
Saturday's protest was one of the largest since a series in 2011 staged by a group calling itself "the indignant ones." The protests two years ago -- before Rajoy came to power 14 months ago -- were in response to the Socialist government's harsh austerity policies to address the country's mounting national debt.
Though Rajoy has said the austerity measures have helped steady an economy on the brink of collapse, the lack of government spending resulted in mass layoffs. Spain's unemployment rate is 26 percent, CNN said.
He defended his government's actions in a speech to the nation Wednesday.
"We have left behind us the constant threat of imminent disaster and are starting to see the path for the future," Rajoy said
But many average Spaniards weren't buying it.
"I hate to think he was taking illegal money," said Luis Garcia, a 63-year-old welder at a defense plant who voted for Mr. Rajoy. "But the official explanations don't add up."