People in Guernsey are being asked to work from home after the number of Omicron cases in the island doubled from three to six in 24 hours.
Mandatory mask use has also been extended to cinemas, theatres, concert venues and places of worship.
Announcing the new restrictions tonight, the Civil Contingencies Authority (CCA) - the island's emergency decision-making group - said there was "the potential to see a large wave [of Omicron] in the Bailiwick in the coming weeks."
The CCA said: "Increasingly, data indicates a more transmissible variant that will spread quickly leading to significantly higher case numbers than have been seen under other variants, both globally and here in the Bailiwick.
"Currently, the hospital and other health services are preparing for a potential increase in covid patients. However, they do not expect the increase in hospital admissions to be as severe as the increase in overall cases. This continues to be kept under review as more data emerges, but the services are currently confident they are well prepared and will be able to manage.
"The top priority now is to deliver the booster programme as quickly as possible to minimise the numbers of cases requiring hospital or medical treatment."
Video: The CCA's latest covid briefing.
Earlier today, Guernsey's Education Committee decided that States' schools would break up for the holidays after school on Friday this week rather than on Wednesday next week as originally planned. In Jersey, schools are already due to break up on Friday.
According to official statistics published this evening, a total of 677 people have tested positive for covid in Guernsey and 1,029 in Jersey.
Omicron reached Guernsey last week, but is yet to be detected in Jersey. The island's positive test samples are being sent to the UK for sequencing, but turnaround takes roughly 72 hours.
Earlier today, the Jersey Symphony Orchestra announced that it was cancelling its long-awaited return to the stage after 10 of the 30 musicians due to travel to the island to take part had to withdraw due to the Omicron variant.
Express has asked whether Jersey's Competent Authority Ministers (CAM) - who have the final say on covid decisions - will be meeting to discuss potential changes to the island's strategy in light of the Omicron threat, and is awaiting a reply.
After Prime Minister Boris Johnson announced 'Plan B' for limiting the spread of covid in England last Wednesday, CAM held an urgent meeting, but decided against imposing any new covid restrictions.
Yesterday, Boris Johnson said that the variant was "spiking" in London, making up 40% of all covid cases in the capital. He predicted that it would make up more than half of all London's covid cases by the end of the week.
Currently, travellers arriving in Jersey from the UK, Ireland, Isle of Man or Guernsey - who haven't been anywhere else in the previous 10 days - do not have to undergo a PCR test at the border.
On Monday, Deputy Medical Officer of Health, Dr Ivan Muscat MBE, urged eligible islanders to get a booster dose of the vaccine, saying it was the best way to protect against the Omicron threat.
Pictured: Dr Ivan Muscat urged islanders 30 and over to get a third dose of the covid vaccine.
He explained: "The current estimates also find that a full two-dose vaccination course alone is less effective against symptomatic disease with Omicron than with the original strain of covid-19 or the Delta variant. The rate of waning is unknown at the moment. Protection by the booster against severe disease is likely to be higher but this has yet to be confirmed.
“While islanders over the age of 40 who are unvaccinated or not boosted are at highest risk of hospitalisation, islanders under 40 who are unvaccinated or not boosted are still very much at risk of illness, spreading the virus in the community, and suffering from complications of Long Covid.
“If you are aged 30 years or over, you can book your covid-19 booster NOW. I urge anyone in this age group who has not booked to act now before we see the effects of Omicron in Jersey.”
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