Omicron is now the dominant strain of coronavirus in Scotland, Nicola Sturgeon said as she warned a “tsunami” of the variant is hitting the country.

The First Minister said 51.4% of Covid-19 cases in Scotland are now likely to be Omicron.

The R number, which measures the rate of infection, could be above four and cases of the virus have increased by more than 40% in the past week, the First Minister said during a coronavirus briefing.

She urged people to stay at home in the run-up to Christmas, saying the emergence of Omicron has been the “cruellest of blows”.

“The tsunami I warned about a week ago is now starting to hit us,” she said.

“However, and this is a key point, a really key point actually, we shouldn’t be fatalistic about this. We are not powerless in the face of it.”

The First Minister said it “seems that boosters are still very effective in reducing the risk of falling seriously ill from Omicron”.

She said it is expected the increase in cases will “continue and accelerate”, and stressed the need to slow down the spread of the virus, adding: “As of now the scale and the immediacy of the challenge it presents is of profound concern.”

On Friday, new guidance in Scotland came into force to prevent further spread of coronavirus.

Businesses across the country are legally required to take “reasonable measures” to minimise transmission of the virus.

Advice includes a return to one-way systems in premises, app-based ordering and the use of screens at service points.

The hospitality sector has been encouraged to return to table service where practical and to consider measures to reduce crowding.

Earlier, Scotland’s Finance Secretary Kate Forbes said the Scottish Government is calling on the UK Treasury to “step up and provide urgent funding” to businesses.

At the coronavirus briefing, Ms Sturgeon claimed it would be “unconscionable” for the Treasury not to provide more support given the rapid spread of Omicron.

She announced that of the £100 million Scottish Government money being allocated “for the impact businesses are already suffering”, £66 million will go to the hospitality sector, £20 million for culture, £8 million to the food and drink supply chain, and £3 million each for the wedding and tourism industries.

Asked where she would spend any additional money from the Treasury, Ms Sturgeon said she wants to be “able to take decisions I think appropriate without worrying about not being able to compensate businesses”.

Ahead of a call with Prime Minister Boris Johnson, Ms Sturgeon said: “There has to be a systemic approach to this where we know that, if we have to take difficult public health decisions, support kicks in behind that and it kicks in whether it’s Scotland, Wales, Northern Ireland, or England making these decisions and not just – as is the case just now – only when the UK Government for England takes those decisions.”

Highlighting that the UK Government is able to borrow money rather than take it from existing budgets, she added: “If I have the borrowing powers the Treasury had, I would be able to do that and it’s a sensible thing to be doing right now to help shield the economy from the pressures of this.

“I don’t have those borrowing powers so I can only look to the Treasury to use them.

“It will be unconscionable, frankly, given what we’re facing right now if the Treasury doesn’t very quickly start to use these things.”