A man (60) is said to have killed his girlfriend (71) in her apartment in Cologne according to his own statement in a dispute.
The man came to the nearest police station on Friday after the crime and described the argument, the investigators said.
Rescue workers alerted by the police had tried in vain to reanimate the woman.
A homicide squad has started the investigation.
Cologne - The man was temporarily arrested and is to be questioned first.