The recommendations apply initially to Oslo and the Indre Østfold municipality as well as to journeys to and from these locations.
They take effect for an initial 14 days.
The new guidelines on face masks are a recommendation and therefore not a mandatory requirement which authorities can enforce.
Norway’s Directorate of Health (Helsedirektoratet) is confident that members of the public will understand the seriousness of the situation and follow the recommendations, the authority’s director Bjørn Guldvog said to VG.
“It’s not relevant to use the police to control compliance with this recommendation. Local transport companies can decide whether to use security personnel or other staff to advise passengers,” he said.
Operating company Ruter is responsible for the running of buses in Oslo. The firm’s press spokesperson Knut-Martin Løken told VG that Ruter does not have the authority to enforce either the wearing of face masks or sanctions for not wearing them.
“This is a recommendation and not a law,” Løken told the newspaper.
As such, passengers who use buses, trams or underground rail in Oslo will not be asked to disembark if they refuse to wear face masks, he confirmed.
Information posters outlining face mask recommendations will be placed by Ruter on board buses, trams and underground T-bane trains.
National rail operator Vy will, like Ruter, not ask passengers to leave trains if they do not wear face masks.
“This is voluntary. It is passengers’ own responsibility to wear a face mask and keep a one-metre distance,” Vy head of communication Nina Schage told VG.
“If (the train) is full, we encourage you to consider a different departure,” she added.