One person was wounded in an attack in Cologne city center in the early hours of Monday, a police spokeswoman said, adding that there were no signs of a terrorist motive.
Local newspaper Express described it as a knife and gun attack. The police spokeswoman said she was awaiting clarification from the hospital the injured person was taken to before confirming what type of weapons were used.
She said police received emergency calls at 3.45 a.m. (0145 GMT) reporting that several people were involved in an argument and police found blood and broken panes of glass at the scene.
There has been a spate of indiscriminate attacks against civilians in Germany in recent weeks, two claimed by the Islamic State group, and a mass shooting in Munich initially seen as terrorism-related.
The spokeswoman said the number of people involved in the Cologne incident was unknown.
She said eyewitnesses had reported seeing two cars speeding away but declined to confirm, as Express reported, that two suspects were on the run.