The trouble started when police tried to clear the protesters from a main square in Barcelona so sanitation workers could clean it up before possible celebrations after a soccer match Saturday night.
Many of the protesters, who are angry about high unemployment, anti-austerity measures and politicians' handling of the economy, refused to move. Television images showed officers beating the demonstrators and dragging them on the ground. Some wound up with bloodied hands and heads, or broken limbs.
Catalonia regional Interior Ministry spokesman Felip Puig said 84 protesters and 37 police were injured. Officers were seen hauling people away, but Puig did not say how many had been arrested and he didn't say how serious the injuries were. He did say one protester had a broken arm.
The protesters were allowed to return to the plaza, which has been occupied by protesters for nearly two weeks, after it was cleaned. Protesters have been camped out there for nearly two weeks. Puig justified the authorities' action by saying the plaza had to be cleaned because soccer fans will gather there Saturday night after the Champions League final between Barcelona and Manchester United in London.
Scuffles also broke out between authorities and protesters in the city of Lleida, west of Barcelona. Two people were arrested, according to the Europa Press news agency.
United behind the slogan "Real Democracy Now", tens of thousands of mostly young people have set up round the clock protest camps in cities and town across Spain since May 15 to voice their discontent over the government's handling of the economic crisis and what they see as a corrupted political party system.
Nearly two years of recession has left Spain with a 21.3-percent unemployment rate, the highest in the eurozone, and major debt problems. The rate jumps to 35 percent for people ages 16-29, and many young and highly educated Spaniards can't find jobs as the eurozone's No. 4 economy struggles to emerge from a two-year recession.
The biggest protest has been in Madrid's Puerta del Sol square, where tens of thousands of people showed up for nightly protests for nearly a week before regional elections last weekend. On Friday, about 500 people were still camping in the plaza, but they indicated they might move on within several days.
Riot police have monitored the Madrid protesters, but have not intervened. Interior Minister Alfredo Perez Rubalcaba said Friday he was reviewing a request by Madrid's regional government to dismantle the city's protest zone because of complaints by merchants that business is suffering in the key tourist area.