Violence at a disputed Eritrean music festival in the German town of Giessen has left 22 police officers wounded.
Law enforcement officers fired tear gas and used water cannon to quell the unrest.
Videos showed throngs of men shouting and running on streets.
"Twenty-two police were injured, mainly in incidents of stone throwing," regional police said on Twitter.
About 1,000 police were deployed in this town of 80,000 residents north of Frankfurt after last year's festival descended into violence.
Between 2,000 and 3,000 people had been expected to attend this year's event, due to run until Sunday. Police did not give details of any arrests.
Clips posted on Twitter appeared to show several men sitting on the ground with their hands in handcuffs.
Officers in riot gear could be seen attending to one man who appeared to be unconscious.
The organisers are accused of being close to the authorities in the small and secretive one-party African state, where critics are sent to prison and civilians are conscripted for life or forced into labour under an extreme policy of national service.
Eritrea has been sanctioned for meddling in regional conflicts.
The Red Sea nation broke away from Ethiopia in May 1991 and formally declared independence on May 24, 1993. It is led by Issaias Afeworki, who is known for his authoritarian rule.
