Spaniards protesting over the handling of the country's economic crisis vowed to keep their tents in Madrid's Puerta del Sol square this week, driving a movement that is spreading across Europe.

Dubbed "los indignados" (the indignant), tens of thousands of demonstrators packed squares across Spain in a wave of outrage over high unemployment and government austerity measures in the run-up to local and regional elections on May 22.

The elections, took place late on Sunday, dealt a crushing defeat to Spain's ruling Socialists, who have had to balance voter anger over national belt tightening and investor demands for strict measures to keep the public deficit in check.

The "Real Democracy Now" movement, also coined the "Spanish Revolution", has inspired similar demonstrations in Paris and Athens.