“Two people have been confirmed dead in the shooting episode. There are several seriously injured. The police defined the mission as a PLIVO incident,” OPS Police Oslo said in a series of tweets.

Three injured persons were reported to be in critical condition. Police have arrested one suspect.

The crime scene extended from the London Pub via a neighbouring club and onwards to a nearby street where the suspect was apprehended with assistance from civilians and guards a few tens of meters away, police spokesman Tore Barstad told Norwegian newspaper Aftenposten.

“We have technicians inside him now who are working with investigations,” duty officer Roger Hjerto at the crime watch at the Oslo police told broadcaster NRK.

On Saturday night, the police took action against addresses related to the man to look for a possible motive for the incident.

“This is a very serious incident that shakes us all. My thoughts go to those killed and injured and all affected. Norway is a community of trust where everyone should feel safe outside on a Saturday night. The police have arrested a suspected perpetrator, and are now working to clarify the actual circumstances,” Minister of Justice and Emergency Preparedness Emilie Enger Mehl (Sp) said in a statement on Aftenposten.