Sixty people were injured and 11 arrested when hundreds of youths hurled bottles and burned bins in clashes with police outside a music festival in Madrid on Saturday, officials said.
Youths rioted when they were turned away from the MTV Madrid Beach open air festival in western Madrid early on Saturday because the concert area was full, a police spokesman said.
He described the incidents as "unusual" in their scale and intensity.
Disturbances spilled into nearby streets and lasted about four hours, involving about 1,000 youths with dozens of police deployed, the spokesman, who asked not to be named, told AFP.
"Various people tried to enter the festival but the venue was full. There were disturbances and containers were set on fire" and bus stops trashed, he said. "There was a shower of bottles," he added.
"The city police was overwhelmed and called for reinforcements from the national police."
Media reports said police fired rubber bullets and charged at rioters.
The spokesman said 60 people were injured, most of them lightly. Those injured included 20 police officers of whom two were taken to hospital.
An emergency services official separately told RNE national radio that among the 60 injured, 10 people were taken to hospital overall.
The 11 people arrested were being charged with assaulting police officers, the police spokesman said.
The last comparable clashes in Madrid broke out over recent months on the fringes of mass demonstrations against economic measures taken by the government in Spain's recession.