A new rule mandating airline passengers traveling from China to South Korea to show negative COVID-19 test results before entering the country was applied Thursday, as the government expressed concerns over an uptick in imported virus cases from the neighboring country.

For the next two months, all passengers arriving from China must either present a negative PCR test result conducted two days before departure or a rapid antigen test result taken within 24 hours before boarding.

Passengers entering Korea for business trips, humanitarian purposes, children under the age of six and those diagnosed with the virus within 10 to 40 days are not subject to the mandate.

The toughened rule is part of the country’s efforts to prevent an influx of confirmed patients flowing into the country, as it saw a rapid spike in cases from China, according to the Korea Disease Control and Prevention Agency.

Of the 194 imported cases reported Thursday, 137 came from China, accounting for nearly 70 percent of the cases, the KDCA said.

Last month, China lifted its draconian “zero-COVID” policy amid widespread protests from locals. Under the relaxed measures, frequent coronavirus tests and health codes are no longer required for daily life or to travel within the country.

Since pivoting away from its strict pandemic-related restrictions, a surge in infection cases has overwhelmed China, resulting in a shortage of beds and medicine.

As virus woes are growing over China’s stark increase in virus cases, the government has been implementing tightened quarantine restrictions for entrants from China since Monday.

All incoming passengers are required to undergo PCR tests upon arrival, and short-term visas for Chinese nationals are restricted until the end of this month. Flights to South Korea from China are only permitted to land at Incheon Airport.

Travelers from Hong Kong and Macao must also submit negative pre-entry virus tests starting Saturday.

The quarantine measures were initially not applied to travelers from the two autonomous regions. However, health authorities on Tuesday announced that passengers from Hong Kong and Macau must also show negative test results over the possibility that passengers from China might travel through those places to avoid the new rules.