Hundreds of German police have used batons and pepper spray to quell crowds targeting an Eritrean cultural festival in the central town of Giessen.
The protesters were angry that the festival went ahead in Giessen, calling it a propaganda exercise by the authoritarian Eritrean regime.
A police statement said clashes took place for hours on Saturday, and that 26 police officers were injured.
Police arrested nearly 100 people and had to stop traffic in the town centre.
The police statement said protesters threw bottles and stones at police, damaged some vehicles and ripped down fencing around the festival venue.
They also threw stones at buses carrying participants to the festival, the statement said.
Video on Twitter appears to show crowds of protesters engaged in running battles with police in the town.
The town authorities had tried to stop the festival going ahead after similar unrest erupted last year, but a local court overturned the ban.
Giessen has about 84,000 residents and lies roughly 50km (30 miles) north of Frankfurt am Main.