All Nippon Airways Co. and Japan Airlines Co. said Wednesday they have stopped accepting reservations for inbound international flights to Japan in line with a government request to stem the spread of the Omicron variant of the novel coronavirus.

The transport ministry said it had asked airlines to stop accepting reservations for such flights until the end of December, while Chief Cabinet Secretary Hirokazu Matsuno said Japan will deny entry to all foreigners from 10 African countries feared to have outbreaks of the variant.

The move comes as Japan confirmed its second case of the potentially highly contagious strain the same day -- a man in his 20s who arrived at Narita airport near Tokyo on Saturday after recently staying in Peru, Matsuno said at a press conference.

The man, who is fully vaccinated with Pfizer Inc.'s COVID-19 vaccine, was initially asymptomatic but later developed a fever and sore throat. Around 114 people who were on the same flight as the man have tested negative and are being treated as close contacts.

Japan confirmed its first case of infection involving the variant, a diplomat in his 30s traveling from Namibia, a day earlier. The man from Peru, who is currently in quarantine at a medical facility, was not in close contact with the diplomat, according to a government source.

Scientists are trying to determine whether the highly mutated strain is more transmissible than the existing Delta variant of the coronavirus or able to evade immunity from vaccines or previous infections.

The Omicron variant was first reported by South Africa last week and has been discovered in a number of African and European countries as well as Canada, Israel and Hong Kong.

The Ministry of Land, Infrastructure, Transport and Tourism's request to stop taking reservations for inbound international flights means all Japanese citizens and foreign residents will effectively be locked out of the country.

Japan will also deny re-entry to all foreigners, including residents with long-term visas, who have recently been to Angola, Botswana, Eswatini, Lesotho, Malawi, Mozambique, Namibia, South Africa, Zambia and Zimbabwe.

The measure will come into effect Thursday and remain in place "for the time being," Matsuno said. Japan has already banned new entries of foreigners from around the world.

Japanese expats and travelers were shaken by the sudden border restrictions, with many anxious about whether they will be able to return home.

"I'm surprised the Japanese government has suddenly tightened the rules. I definitely want to spend New Year's Eve at my parents' house," said a 29-year-old Japanese woman working at a cafe in Vancouver, Canada, who has been looking forward to returning home for the first time in three years.

Liu Chao, 35, who was at Kansai International Airport in Osaka Prefecture to pick up his wife and daughter arriving on a flight from Hong Kong on Wednesday evening, said while he understands Japan needs the restrictions as measures against the new variant, he wishes the government "would take into consideration the families of foreign workers."

Exemptions will be made in "special circumstances" involving foreign spouses and children of Japanese citizens, diplomats and humanitarian cases.

But Matsuno said Japan is narrowing eligibility for such exemptions as part of efforts to keep out the Omicron variant and has stopped accepting government-funded international students or participants in the Japan Exchange and Teaching Program.

The World Health Organization has designated the strain a "variant of concern," warning it is likely to spread globally and poses a "very high" risk.

On Tuesday, however, the WHO urged against implementing blanket travel bans, saying they will not only be ineffective in preventing the global spread of the variant but also "place a heavy burden on lives and livelihoods."

In addition to the ban on new entries of foreigners, Japan has imposed tougher quarantine measures for Japanese citizens and foreign residents who have recently been to certain countries or regions, requiring them to spend up to 10 days of their two-week isolation periods in government-designated facilities.

On Wednesday, the Foreign Ministry said people returning from South Korea will now be subject to a six-day quarantine in government-designated facilities, while six days -- up from three days -- will also be required for those from Australia, Germany, Sweden and Portugal.

The ministry said three days will now be required for those from Switzerland, as well as the Canadian provinces of Alberta, Quebec, and British Columbia, and the French territory of Reunion.

The measure due to heightened concerns over the Omicron variant comes into effect starting Friday.

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