Large numbers of riot police were seen heading to the scene after violence broke out at an open-air party in Frankfurt city centre, in the early hours of Sunday morning.
Police reportedly went into action after a reveller appeared to be injured after the mood soured and a mass brawl broke out at a gathering in the city's Opernplatz.
Officers attempting to help were reportedly turned on by multiple party-goers who hurled bottles and glasses at them while bystanders applauded and chanted anti-police slogans.
Authorities subsequently cleared the square, with the incident set to be discussed at a security conference in the city on Monday.
Last month rioting and looting also took place in Stuttgart when several hundred people rampaged through the city after police performed checks on people suspected of using drugs.