Scots are to be ordered to stay at home amid a fresh Covid-19 lockdown which will see schools remain closed to pupils until February.
First Minister Nicola Sturgeon said new curbs would be introduced at midnight in a bid to contain the new, faster-spreading strain of the virus.
New laws will require people to stay at home and work from home where possible.
Outdoor gatherings are also to be cut back, with people only allowed to meet one person from one other household.
Places of worship are to be closed, group exercise banned, and schools will largely operate via online and remote learning.
These rules will apply across the Scottish mainland until at least the end of January, and will be kept under review.
Island areas will remain in level three – but Ms Sturgeon said they would be monitored carefully.
A further 1,905 new cases were reported on Monday – with 15% of tests returning a positive result, something Ms Sturgeon said “illustrates the severity and urgency of the situation”.
The first minister said she was “more concerned about the situation we face now than I have been at any time since March last year”, with the new coronavirus strain now accounting for half of new cases.
And she said a “steeply rising trend of infections” was threatening to put “significant pressure” on NHS services, saying hospitals could breach capacity within three to four weeks.
The new rules – which will be put down in law – mean Scots will only be allowed to leave home for essential purposes, such as shopping for food and medicine, exercise and caring responsibilities.
No limit is to be put on how many times people can go out to exercise, but outdoor meetings are to be limited to a maximum of two people from two households.
Everyone who can work from home will be required to, and people in the “shielding” category are advised not to go in to work at all.
The construction and manufacturing industries will remain open, but Ms Sturgeon said this would be kept under review.
Places of worship are to close, the number of people who can attend weddings is to be cut to five, and funeral wakes will no longer be allowed.
Schools are to remain closed to the majority of pupils until February, with Ms Sturgeon saying community transmission of the virus must be brought to a lower level amid concerns that the new variant of the virus spreads more easily among young people.
She said she knew remote learning presented “significant challenges” for parents, teachers and pupils, adding: “I want to be clear that it remains our priority to get school buildings open again for all pupils are quickly as possible and then keep them open.”
The first minister said she was considering whether teachers could be given the Covid-19 vaccine as a priority.
More than 100,000 people have been given a first dose of the vaccine in Scotland, and the government expects to have access to just over 900,000 doses by the end of January.
However Ms Sturgeon said the best way to get schools open again was to drive down transmission of the virus – urging Scots to abide by the rules.