A suspect has been arrested after the incident in the Kuecknitz district of the city, north-east of Hamburg.
Police spokesman Duerk Duerbrook said authorities are still trying to determine the circumstances of the attack.
Local daily Luebecker Nachrichten reported that a suspect had attacked passengers with a knife.
The perpetrator is believed to have been apprehended, but not before 14 people were wounded, at least three of whom are believed to have suffered serious injuries.
State police tweeted: “Nobody was killed. The perpetrator was overpowered and is now in police custody.”