Scotland reported six Omicron cases on Monday, some not linked to travel in southern Africa, raising concerns that the mutation-heavy coronavirus variant is already spreading in the community.

Britain as a whole has reported nine cases of the new variant, which the World Health Organization said on Monday was likely to spread internationally and posed a very high risk of infection surges. read more

The four nations of the United Kingdom have all restricted travel to southern Africa, where the variant was first detected last week, in a bid to slow its spread.

But Scottish First Minister Nicola Sturgeon said not all of the six cases had recent travel history or known links with others who had travelled to southern Africa.

"This suggests that there might already be some community transmission of this variant," she told a news conference.

"There is no evidence yet that this is sustained, nor any evidence from the enhanced surveillance that it is widespread at this stage."

Sturgeon said the timeframe of the cases suggested it was unlikely but not impossible that there was a link to the COP26 climate change conference that took place in Glasgow earlier this month.

COMING HOURS

British Prime Minister Boris Johnson has responded to the emergence of Omicron by making mask-wearing compulsory in shops and on public transport in England.

He also asked the Joint Committee on Vaccination and Immunisation (JCVI) to review the booster programme for under-40s, and look at reducing the gap between second and third vaccine doses.

"We'd expect that (review) within the coming hours," junior health minister Edward Argar told Sky News.

Ministers and scientists say even if vaccines prove to be less effective against Omicron, they should still offer protection against it and help keep a lid on numbers of hospitalisations and deaths.

Anthony Harnden, deputy chair of the JCVI, said that given it would take time to develop a variant-specific vaccine, raising immunity in the population was advisable.

"Inevitably, everybody will be offered a booster, but what we want to do is make sure that it's done in a sensible order," he told BBC TV.

Scientists say Omicron has about double the number of mutations to the spike protein as the currently dominant Delta variant.

Argar said that cases would inevitably rise further, but "we don't know by what speed or by what numbers ...We're trying to give ourselves the time to understand how it works and how it interacts with the vaccine."