Thousands of people massed in central Madrid for a rally organized by radical Spanish leftists Podemos.
The "March for Change" is one of the party's first outdoor mass rallies, as it looks to build on the recent victory of its close allies Syriza in Greece, BBC reported.
According to the party's leader, Pablo Iglesias, the march's aim is not to protest or ask the government for anything, but to mark the beginning of change.
Following the victory of radical left-wing Syriza party, Iglesias told Rajoy to "begin the backwards countdown," according to media reports.
"Today Greece said that yes it is possible. It is the same as we shall say in Madrid on the 31: we can build a fairer country," Podemos said.
According to Iglesias, Spain's economic woes are because of "a corrupt minority which has committed the biggest plundering in Spain's recent history."
Syriza won in Greek parliamentary elections on January 25. The anti-austerity party received 36.34 percent of votes.
The Syriza party aims to renegotiate the austerity measures imposed by the European Union and International Monetary Fund (IMF) creditors, worth about $268 billion.
Many Spaniards are enraged over reports of political corruption and public spending cuts implemented by the governing People's Party and previous administrations.
The two big traditional parties have described the party - less than a year old - as populist.
Prime Minister Mariano Rajoy warned Spaniards not to "play Russian roulette" by supporting the newcomer, which he said "promises the moon and the sun" but cannot deliver them. Spain has now officially come out of recession but nearly one in four workers remains unemployed.
Last year was the first time there has been full-year economic growth in the country since 2008, when a property bubble burst, putting millions of people out of work and pushing the country to the brink of a bail-out.
