Madrid , Spain ( CNN ) -- Protests against Spain 's economic crisis took a new turn Wednesday as social media networks fueled calls for demonstrators to take to the streets before local elections a few days away . Thousands returned late Tuesday to Madrid 's central Puerta del Sol plaza -- where the main protests began Sunday . A few hundred demonstrators camped out there overnight , while similar but smaller protests were held in Barcelona and other Spanish cities , a protest organizer said . `` The economy and unemployment are key to the protest because that binds all of us together , '' said Jon Aguirre Such , a spokesman for the Real Democracy Now , one of many groups convening the demonstrations . `` In this crisis , while some have gotten rich , most people have less income , '' Aguirre said . Demonstrators are protesting Spain 's 21 % unemployment rate and a record 4.9 million jobless . Protesters say a plethora of temporary labor contracts offer few or no job benefits . In addition , some are protesting against the political and financial establishment that they say is to blame . The protests come in the closing days of the campaign for local elections set for Sunday . Spain 's 8,000 cities and towns will elect mayors , along with 13 ( out of 17 ) regional presidents and parliaments . Opinion polls in Spanish media predict major gains for the opposition conservatives over Prime Minister Jose Luis Rodriguez Zapatero 's ruling Socialist party . Zapatero , squeezed by the nation 's prolonged economic crisis , announced last month he wo n't seek a third term in national elections due by March 2012 . For the past few years , as Spain 's rate of unemployment remained tenaciously high , most of the protests were organized by major trade unions . But the latest protests appear to be grass-roots movements fueled by social networks , sparking more attention . Elena Ortega , who says she 's managed to find only a part-time secretarial job , helped spread the word on Facebook about the protests on Wednesday . `` If this is happening , it 's because the unions were n't doing what was needed , when it was needed . They have n't delivered , '' she said . She said she 's worried about her 20-year-old son , who has only found temporary jobs in the past four years . `` Forty percent of our young people are unemployed and do n't have a chance , '' Ortega said . The movement does not appear to be linked to the unions or political parties , the traditional protest heavyweights in Spain , said Economist Fernando Fernandez of the IE Business School in Madrid . `` I think we really do n't know what we 're seeing , '' Fernandez said . `` This is the very beginning of a new movement . I do n't expect it to become a very large social response or protest against the unemployment perspective in Spain . '' But hours later , on Tuesday night , several thousand protesters returned to Madrid 's central plaza . By Wednesday morning , dozens remained in their overnight encampment . The social media networks call for renewed protests on Wednesday evening in Madrid and three dozen other Spanish cities . The aim is to continue the protests at least through the elections on Sunday , Aguirre said . But Wednesday afternoon , Madrid 's elections board banned the planned demonstration at 8 p.m. ( 2 p.m . ET ) at the Puerta del Sol plaza . The board said there were not `` extraordinary and serious reasons '' to allow the demonstration on short notice , according to the central government 's main regional office in Madrid . The election board vetoed the demonstration -- which would have come during the final days of the election campaign -- on the grounds it could affect the right of citizens to vote freely , a regional office spokesman said . Organizers of many large demonstrations in Madrid seek and receive prior authorization , usually days or weeks ahead of the event . But the economic protests since Sunday have sprung up on short notice . Spain 's El Pais newspaper reported that authorities planned to have sufficient police officers on hand to prevent the demonstration .
NEW : Madrid 's election board bans demonstration planned for Wednesday evening . Thousands return late Tuesday to Madrid 's central Puerta del Sol plaza . A few hundred demonstrators camp out overnight . Demonstrators are protesting Spain 's 21 % unemployment rate .