Spain's 'los indignados' are outraged over economic stagnation. The banner reads "Let's go to the square". [REUTERS]

Riot police firing rubber bullets and wielding truncheons have clashed with protesters as authorities cleared away a makeshift camp set up as part of a Spain-wide demonstration against the country's economic problems.

Friday's altercation left more than 100 people, including policemen, injured.

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 football match on Saturday night.

Many of the protesters, who are angry about high unemployment, anti-austerity measures and politicians' handling of the economy, refused to move.

TV images showed officers beating the demonstrators and dragging them on the ground. Some wound up with bloodied hands and heads, or broken limbs.

Match forced evacuation

Felip Puig, the spokesman for Catalonia's regional interior ministry, 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 did not say how serious the injuries were.

He did say one protester had a broken arm. "I can assure you that there was aggression against the police with rocks, bits of wood, blows, shoves, with violence, with sprays," Puig said.

He said police had fired six rubber bullets, 12 unspecified "projectiles" and 236 rounds of blank warning shots.

The protesters were allowed to return to the plaza, which has been occupied by demonstrators for nearly two weeks, after it was cleaned. Reports say the projectiles were rubber balls.

Puig justified the authorities' action by saying the plaza had to be cleaned because football fans will gather there on 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 reportedly arrested.

United behind the slogan "Real Democracy Now", tens of thousands of mostly young people have set up around-the-clock protest camps in cities and towns across Spain since May 15 to complain about the government's handling of the economic crisis and what they see as a corrupted political party system.

Growing  debt, unemployment

Nearly two years of recession have left Spain with a 21.3 per cent unemployment rate, the highest in the Eurozone, and major debt problems.

The rate jumps to 35 per cent for people aged 16 to 29, and many young and highly educated Spaniards can't find jobs as the Eurozone's No. 4 economy struggles.

The biggest protest has been in Madrid's Puerta del Sol square, where tens of thousands of people held 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.

Alfredo Perez Rubalcaba, the interior minister, said 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.