About 200 demonstrators with posters gathered in the area of a defense industry company early Friday morning, the police said in a statement.
According to the Welt newspaper, the demonstration was organized by the anti-militarist alliance Rheinmetall entwaffnen (Disarm Rheinmetall), which opposes the supply of weapons by Rheinmetall and other companies, including in the light of the Ukrainian conflict.
The police used pepper spray and batons to defend against attacks from protesters.
"Eight police officers were slightly injured," the statement read.
The police noted that law enforcement agencies will be on duty on Saturday as the demonstrations will continue.