TOKYO - Japanese Prime Minister Fumio Kishida said on Monday that the government will ban the entry of all foreign nationals in principle from Tuesday amid concerns over the new Omicron variant of the COVID-19.

Kishida told local media that the decision was made to avoid the worst-case scenario, adding that "it is a temporary measure until information about the Omicron variant becomes clear."

Japan will also suspend the recent easing of entry restrictions made on Nov. 8, which has allowed vaccinated business travelers to take a shorter quarantine period and started to accept entry applications for students and technical interns on the condition their host organization agrees to take responsibility for monitoring their movement.

Japan has already suspended the exemption for people who have recently been to any of nine African countries, Botswana, Eswatini, Lesotho, Malawi, Mozambique, Namibia, South Africa, Zambia and Zimbabwe.

Kishida said a person who has arrived in Japan from Namibia has tested positive for the COVID-19, however, it will take four to five days to verify which variant the person is infected, local media reported.

According to the health ministry, the man arrived at Narita airport from Namibia on Sunday.

The Omicron variant was first reported to the World Health Organization (WHO) by South Africa last week. So far, several European countries as well as countries and regions including Australia, Canada, Israel and China's Hong Kong have confirmed infections of the variant.

The WHO has named the strain that contains a large number of mutations a "variant of concern," warning it may be highly transmissible and pose an increased risk of reinfection to people who have previously been infected with the COVID-19.

Kishida said the government will begin administering booster shots next month as planned, even though it is not yet known whether current vaccines are effective against the new variant.