On Monday, the Japanese Health Ministry said three cases were recorded in Shizuoka among people aged between 20 and 70. None of the infected patients has ever been to the UK, however, they may have been in contact with those who have. The matter is being investigated.
Meanwhile, the southernmost prefecture of Okinawa is preparing to introduce its third state of emergency since April due to a surge in COVID-19 cases, according to the newspaper Ryukyu Shimpo.
The Japanese government has already declared a state of emergency in 11 of its 47 prefectures, which will last through 7 February.
The number of critically ill patients in Japan has exceeded 1,000, marking the highest figure since the beginning of the epidemic. The rise in severe cases in the country has been observed for 17 consecutive days.
So far, the country has registered over 331,000 COVID-19 cases and as many as 4,305 deaths.
Several new mutated COVID-19 strains have been reported across the globe in recent weeks. In mid-December, the UK government reported that a new variant of the disease, which is believed to be up to 70 percent more transmissible, was discovered in southeast England.
Other variants have been discovered in South Africa and Brazil, raising fears over vaccine efficacy.