There are now 336 cases of the new coronavirus variant across the UK, the health secretary says.
There is community transmission of the Omicron coronavirus variant in multiple regions of England, Health Secretary Sajid Javid has confirmed.
He told MPs the variant was continuing to spread “here and around the world” and there were now cases here “with no links to international travel”.
There have been 336 confirmed cases of the highly-mutated variant across the UK, he said, a rise of 90 from Sunday.
There are concerns about how Omicron could interact with current vaccines.
Of the new confirmed Omicron cases, 261 were in England, 71 in Scotland and four in Wales – while Northern Ireland is yet to have a confirmed case.
Scotland’s First minister Nicola Sturgeon has previously said the variant was spreading in the community after a number of cases were linked to events including a Steps concert in Glasgow.
Mr Javid said he could not guarantee the variant would not “knock us off our road to recovery”, and the window between infection and infectiousness may be shorter for Omicron.
He said the government did not have a “complete picture” of whether the variant caused more severe disease or not, or how it interacted with current vaccines.
The health secretary said 10,000 vaccinators were being recruited to bolster the booster jabs programme because “when the virus adapts, we must adapt too”.
He said 350 military personnel would be deployed in England to help give boosters, and more than 100 in Scotland.
Labour shadow health secretary Wes Streeting called on the government to “bring forward common-sense measures” to limit the spread of the new variant ahead of Christmas.
He said the government should introduce a “standard response” to future variants emerging from overseas, including stronger border controls, testing and contact-tracing.
The UK has put restrictions on flights from countries in Africa, with Nigeria becoming the 11th country added to the red list. At the weekend, the government said the majority of Omicron cases identified in England thus far had links to overseas travel from South Africa and Nigeria.
From 04:00 GMT on Tuesday, everyone travelling to the UK will need to take a Covid test before their journey – as well as a test after they arrive.