Police have advised the operation has concluded and trams are once again on the move after the interruption. It was most likely a false alarm.

Exact details of the operation have not been released, but it took place at 3.30pm at the National Library in Kirchberg, which was surrounded by a large number of police vehicles.

Witnesses reported seeing ambulances in the area as well as police cars. The tram circulation was halted completely during the operation. Other sources reported that officers wearing bulletproof vests were seen entering the building.

The operation is said to have concluded by 4pm and the trams are once again on the move after the 20 minute interruption. It was most likely a false alarm but police have not yet communicated the reason of the intervention.