On Tuesday, Japan verified its first case of the Omicron variant of the coronavirus, which occurred in a man who had recently arrived from Namibia. According to Hirokazu Matsuno, chief cabinet secretary, the man in his 30s had earlier tested positive for the coronavirus at the airport.

The patient is staying in a medical facility, and the government is aware of his close contacts, Matsuno said.

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Japan closed its borders to foreigners for at least a month on November 30, adopting one of the toughest measures in the world to prevent the spread of Omicron, a variant identified recently in southern Africa and classified as a "variant of concern" by the World Health Organisation.

Omicron, a potentially more contagious variant, was first discovered in South Africa and has since been found in Australia, Belgium, Botswana, the UK, Canada, Denmark, France, Germany, Hong Kong, Israel, Italy, and the Netherlands.

Prime Minister Fumio Kishida had announced on Monday it would shut its borders to foreigners, but said that "these are temporary, exceptional restrictions that we are implementing for the sake of safety until more information concerning the Omicron variant becomes available."

He did not specify how long the restriction will be in effect. Kishida added that Japanese returning from specific countries would be quarantined in specific facilities.