Spanish police fired tear gas and rubber bullets at anti-fascist protesters in central Madrid last night as they tried to stop a right-wing rally near an immigrant area of the city.
Anti-fascists threw rocks behind burning barricades in narrow cobbled streets and at least one car was set alight.
Some of the hundreds of far-right activists, separated from left-wing protesters by lines of riot police, gave Nazi salutes.
According to a Reuterswitness more than 1,000 anti-fascists gathered to protest the far-right meeting in Tirso de Molina, a few hundred metres from Madrid's main square, after local authorities sanctioned the rally. The violence comes just over a week before Spaniards vote in a general election where immigration has become a major issue for the first time.
Posters had been pasted on walls in the area earlier in the week warning of a racist demonstration. Protesters, joined immigrants, blocked roads leading down into Lavapies, an area with a large African and Chinese populations.
Demonstrators chanted "You shall not pass," and "Brother Carlos, we will not forget you", referring to 16-year-old Carlos Javier Palomino, an anti-racist protester who was stabbed and killed during a confrontation with rival groups last November.
A spokesman for Madrid's ambulance service said nobody had been injured though left-wing media said one protester had been blinded in one eye. Anti-fascist protesters also threw bricks through the windows of several banks and smashed up offices inside, eyewitnesses said.
The number of migrants living in Spain has increased fivefold in the last 10 years and now account for nine per cent of Spain's 45 million people.
The opposition Popular Party calls immigration a "problem" and proposes measures to compel immigrants to integrate, including restricting the use of Islamic headscarves. The ruling Socialist party has dismissed the Popular Party proposals as xenophobic.