Seven people have been injured after a man wielding an axe attacked commuters at the main railway station in Dusseldorf.
German police said a man was arrested after the incident at 9pm on Thursday.
"A person, probably armed with an axe, attacked people at random," they said in a statement.
Earlier reports said two attackers had been arrested, but police said this was not the case.
Three of those who were hurt had suffered serious injuries, and eyewitnesses reported seeing people lying on the ground injured.
The suspected attacker was arrested after jumping off an overpass near the station, police said.
The 36-year-old man, who was described as being from "the former Yugoslavia" and living in the nearby city of Wuppertal, suffered serious injuries and is being treated in hospital.
An axe was recovered from the scene and officers were searching the area in and around the station, which was closed.
Germany has been on a heightened terror alert after a hijacked lorry ploughed into a Christmas market in Berlin, killing 12 people, last year. Islamic State claimed responsibility.