The issue is apparently down to an error in a main switch in the capital area.
The technical problem has impacted S-train traffic in the city and the lines F and Bx are not running at the moment. Furthermore, delays are expected on all trains passing through Østerport and Svanemøllen stations.
Normal train services are expected to resume within two hours or so, according to rail operator Banedanmark.
A number of traffic lights are also down, according to the police, which urged drivers to be vigilant.