From Saturday 23 January, the very strict measures will be introduced across ten eastern municipalities.
Only essential shops can remain open and municipalities will be allowed to close primary schools and switch secondaries to remote learning.
People are being asked to restrict movements and not to eat meals outside their family.
“We are putting in place the strictest measures since last March in 10 districts,” said Health Minister Bent Hoie.
“In some places we are going even further than in March,” he told a press conference, adding that it will make “daily life difficult for many”.
All public events, indoors and outdoors, are cancelled apart from burials. Restaurants will be limited to takeaway services.
Norway's parliament meanwhile said it would reduce its activities to a bare minimum next week, while the country's sport federation cancelled all sporting events in the affected areas.
The measures will remain in force until at least January 31st following the detection of the British variant in a home at Nordre Follo, 30 kilometres (18 miles) from Oslo.
Two pensioners at the home, aged over 90, were found to have died with the variant, the public health institute said on Friday.
A total of 22 employees and 12 retirees have been found to have coronavirus at the home but it has yet to be established if they have the variant.
The authorities have so far been unable to trace the origin of the cluster or a link with Britain.
“We are doing what we can to stop this with strong measures in order to regain control quickly and lift the toughest measures,” the minister said.
The Minister has requested that those who live in one of the 10 municipalities covered by the measures do not travel to other municipalities that are not covered by the measures.
“The effort that everyone who lives in this area in the next few days will make, is an effort for the whole country. It is uncertain to what extent the mutation has spread to other municipalities, and the situation is confusing,” the minister added.
The 10 municipalities covered are:
* All events outside the home are prohibited, both indoors and outdoors, with the exception of funerals and burials.
* Employers must ensure that employees work from home as far as is practically possible.
* Shops are closed. Exceptions are made for grocery stores, pharmacies and petrol stations.
* Grassroots sports for children and adults stopped.
* A stop in other leisure activities (choir, corps, theatre, etc.)
* Everyone should avoid home visits and gatherings in their own homes.
* Exceptions to this include home services and visits to people who are in the last phase of life.
* Single people can be visited by or visit one or two regular friends or one permanent household.
* Children in kindergartens and primary schools can have visits from their own cohort.
* Everyone should avoid travel that is not strictly necessary. Travel to work must be considered strictly necessary.
* The municipalities and county municipalities should introduce reinforced measures on public transport, this may, for example, be that only up to 50 per cent capacity is used.
* One-on-one businesses, such as hairdressers, should introduce reinforced measures such as the use of face masks in situations where it is not possible to maintain a distance of one metre, or to reduce or temporarily remove treatment options that involve close face-to-face contact.
The following businesses and places will also close:
* Restaurants, but take away is allowed
* Swimming pools, water parks, spa facilities, hotel pools
* Places of worship, with the exception of funerals
* Amusement parks, bingo halls, gaming halls, playgrounds, bowling alleys and similar places where entertainment and leisure activities take place
* Cinemas, theatres, concert venues and similar cultural and entertainment venues.
* Other public places and businesses where cultural, entertainment or leisure activities take place that gather people indoors.
Schools and kindergartens: Kindergartens, primary schools and lower secondary schools upgraded to level red in line with the national traffic light model. The municipalities may decide to close the schools and kindergartens if it is necessary to prepare for the red level or if the infection situation requires.
Upper secondary school: Digital teaching should be introduced in upper secondary school in week 4, and a transition to red level in upper secondary school should be prepared from week 5.
Universities, colleges and vocational colleges: Digital teaching will be introduced for all. All teaching and planned events must be postponed or made digital.
The premises at universities, colleges and vocational colleges are closed to all students.