"We're on strike to stop these suicidal policies," said Candido Mendez, head of Spain's second-biggest labour federation, the General Workers' Union, or UGT.
More than 60 people were arrested in Spain and 34 injured, 18 of them security officials after scuffles at picket lines and damage to storefronts.
Protesters jammed cash machines with glue and coins and plastered anti-government stickers on shop windows. Power consumption dropped 16 percent with factories idled.