German police say they now have an armed assailant at Cologne's main railway station "under control" and the woman he took hostage is receiving medical treatment.
She had minor injuries from the incident but he is reported to have serious injuries.
There was a full evacuation of the station, one of Germany's biggest transport hubs.
Local media say the incident does not appear to have been terror-related.
Earlier there were unconfirmed reports of shots being fired.
Police quoted by the Koelner Stadt-Anzeiger daily said a couple were involved, and the man had argued with the woman in a McDonald's restaurant, before holding her in a pharmacy at the station.
Reports speak of at least one explosion during the incident.
Deutsche Bahn cancelled or delayed train services in Cologne during the stand-off.