A new mutated virus strain has caused rapid spread of infection in several parts of the UK.

Analyzes show that the spread has been particularly large in London and the south-east of England - and now further restrictions are being introduced in the regions to stop the spread of infection.

Must stay at home

The areas that were previously included in what is called risk situation 3 will now be upgraded to risk situation 4, said Prime Minister Boris Johnson at a press conference on Saturday afternoon.

- Residents in the areas should stay at home and not travel outside their areas.

Gyms and other non-essential businesses should close and anyone who can must work from home, Johnson said.

The restrictions also mean that the residents are only allowed to meet one person outside their own household, and then outdoors.

"With a heavy heart"

Boris Johnson also urged all residents to limit their travel.

- We ask everyone not to travel outside their cities and preferably not abroad either.

Those living in areas subject to level 4 restrictions are not allowed to travel abroad, Johnson said.

Those who live in level 4 areas are not allowed to hang out with people outside their household during Christmas.

In other areas, three other households only apply during Christmas Day, instead of five days as previously stated.

- With a heavy heart I announce that we can not celebrate Christmas as planned, said Boris Johnson and continued:

- I know how much emotion you invest in Christmas and how important it is for father and grandparents to meet their grandchildren and for families to gather.

I know this is a disappointment, but we must abide by science.

Not believed to affect vaccination

According to Boris Johnson and the British Government's scientific adviser Sir Patrick Vallance, there is no evidence that the new virus strain causes more serious illness or more deaths than the regular covid-19 strain.

The effect of the vaccine is also not believed to be affected.

"There is no indication that the vaccine will not bite this new strain of virus," Vallance said at the press conference.