Travelers to Hong Kong arriving from the United Kingdom will be required to quarantine initially in a government-run isolation facility from December 21, joining 12 African nations and the United States on the Chinese city’s strictest entry tier.

The decision came after UK Prime Minister Boris Johnson on Monday delayed the launch of anti-epidemic measures by a week to December 28, despite a sharp rise of Omicron cases in the country.

During the week ended Monday, the UK recorded an average of 82,808 cases per day, up 62% from the previous week. On Monday, that figure hit 91,734, which reports say might include more than 10,000 Omicron cases.