"The banks and the governments that caused this situation must know that we do not agree with the measures and the budget cuts, that we intend to be heard," the movement known as the "indignant" said in its call for further nationwide protests.
Protesters were converging on central Madrid from six points on the city's outskirts, with the rally near parliament set to begin around 2:00 pm (1200 GMT).
"Organise Yourself and Fight," a lead banner read in a march that set off early Sunday from Leganes, some 15 kilometres (nine miles) south of Madrid.
Protests were also planned in the coastal cities of Barcelona and Valencia, where the movement has staged other demos in recent days against austerity measures and corrupt politicians.
Clashes Wednesday in Barcelona between police and demonstrators that left at least 23 injured prompted organisers to urge restraint on Sunday, while police deployed heavily in Madrid.
Protests over the economic crisis and soaring unemployment began in Madrid on May 15 and fanned out nationwide as word spread by Twitter and Facebook among demonstrators also known as "M-15", "Spanish Revolution" and "Real Democracy Now".
At the peak of the protests ahead of May 22 local elections, tens of thousands of people had packed city squares across Spain to decry welfare cuts, corruption and a jobless rate of 21 percent in the first quarter of 2011 -- the highest in the industrialised world.
The protesters dismantled their camp in Madrid's Puerta del Sol square on June 12 while saying that did not signal the end of their movement.