The fight broke out when a dog belonging to a 32-year-old woman did its business in a local park in Bergisch Gladbach in North Rhine-Westphalia.
A 33-year-old female passer-by, seeing the dog's owner walk on, demanded that she clean up her dog's mess, police said.
When the woman refused a shouting match ensued. Before long the 33-year-old had thrown her keys at the dog owner and hit her on the head. At this point a passing man managed to separate the two women, Die Welt reported.
By this point five people were involved in a full blown fist fight. One person was even using a club, police was quoted as saying by The Local.
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According to town regulations in Bergisch Gladbach, not cleaning up dog poo can carry a fine of 30 euros.
The police are also investigating serious bodily harm due to evidence of serious wounds, swollen arms and ripped out hair as a result of the fight that took place on Sunday.
In April, locals in Einbeck, Lower Saxony, gathered 250 kg of dogs' leavings from the town's parks and hung it round the neck of a famous local statue in protest against lazy owners.