Ultra-conservative Salafist Muslims turned on police protecting anti-Islam protesters in the western German city of Bonn, injuring 29 officers, two of them seriously, police said in a statement on Sunday.
Authorities arrested 109 people, among them a 25-year-old man suspected of stabbing two police officers, after angry clashes on Saturday between protesters waving banners showing cartoons of the Prophet Mohammad and a large group of Salafists.
Local media said 500-600 Salafists faced off with 30 anti-Islam protesters.
The Salafists in recent weeks have handed out thousands of Korans, translated into German, to non-Muslims, sparking a highly charged debate in Germany.
North Rhine-Westphalia Interior Minister Ralf Jaeger pledged to identify all Salafists prepared to use violence, so that authorities could take swifter action in future.