According to Danish rules, entry is stopped if the spread of infection exceeds 30 confirmed cases of infection per 100,000 inhabitants, on average per week.
If a Nordic country as a whole exceeds the limit value, one looks instead at the regional level.
Right now, the spread of infection in Sweden is too high and residents in eight regions are being stopped from traveling into Denmark.
The restrictions include Halland, Blekinge, Stockholm, Jämtland-Härjedalen, Kronoberg, Uppsala, Västmanland and Örebro.
Norway advises against four Swedish regions
At the same time, the Norwegian Ministry of Foreign Affairs has updated its travel recommendations and now advises against travel to Gotland, Värmland, Västernorrland and Norrbotten.
It also introduces travel advice for Latvia, Liechtenstein and Cyprus.
The government has "decided that these countries and regions go from yellow to red on the infection map for Europe", the Norwegian government writes in a press release.
Everyone who travels to Norway from these areas from the night until Saturday 10 October must be quarantined for ten days.