The Japanese government has tightened a ban on the entry of nonresident foreign nationals starting from Monday as coronavirus cases reach record highs and the nation confirmed that infections involve a new and potentially more transmissible variant.

The restrictions will be implemented through late January, the government said in a statement on Saturday. Meanwhile, Japanese nationals and foreigners with residency will no longer be exempt from a 14-day quarantine after arriving, the statement said.

The move came amid mounting concerns over the spread of the new variant of the coronavirus at a time when cases in Japan and its capital city Tokyo reached new highs.

The variant, which led to the lockdown of London and southern England, has been diagnosed in five people in Japan so far, Norihisa Tamura, Japan's health minister, said on Friday. All had either recently traveled to the United Kingdom, or been in contact with someone who had.

Under the move, the Japanese government will require all people coming from countries and territories where the new variant is confirmed to submit negative virus test results within 72 hours of departure and undergo tests upon arrival from Wednesday.

The UK, Germany, France, Switzerland, Ireland and Sweden are among the nations that have confirmed the presence of the new variant.

However, businesspeople and students from 10 countries and regions including China, Thailand, Vietnam and South Korea, with which Japan has a special scheme to ease travel restrictions, will not be affected by the suspension policy.

Starting from Monday, Japan will stop the issuance of new visas but those who already obtained visas will be allowed to enter the country, except for those who were in the UK or South Africa within 14 days, under which case, their application for an entry permit will be rejected.

Atsuo Hamada, a professor at Tokyo Medical University, said Japan should take additional antivirus steps including stronger border controls, on the assumption that the new variant has already entered the country to some extent.

"Once a highly transmissible variant spreads, the number of infections could surpass 2,000 in a single day in Tokyo, eventually necessitating another state of emergency" over the virus, Hamada warned.

A recent study by British scientists, released by the Centre for Mathematical Modeling of Infectious Diseases at the London School of Hygiene and Tropical Medicine, suggested that they found no evidence that the variant is more deadly than others but estimated that it is 56 percent more contagious.

The study warned that the variant is so contagious that new control measures, including closing down schools and universities, might be necessary. Even that may not be enough, they noted, saying, "It may be necessary to greatly accelerate vaccine rollout."

Japan reported 2,937 new COVID-19 cases on Sunday, bringing the country's cumulative total of cases to 221,370. What's further alarming is that a health ministry report showed that seven prefectures of the nation reached their highest level of alert for hospital beds, meaning that the healthcare system in those places is on the brink of collapse.

Globally, more than 80 million people have been infected by the coronavirus as of Sunday, according to a tally by Johns Hopkins University. Among them, over 1.75 million people have died. The virus has been detected in nearly every country and the number of new cases is still growing worldwide, with more than 500,000 reported each day on average.

Agencies contributed to this story.