China has stopped issuing short-term visas to individuals from South Korea and Japan in retaliation for Covid restrictions on Chinese travellers.
Visas for South Koreans entering China as tourists have been suspended, Beijing's embassy in Seoul said.
And Japanese media reported China was imposing similar measures there.
It's a tit-for-tat move which Beijing says will remain in place until "discriminatory" entry restrictions against China are lifted.
Last week, South Korea stopped issuing tourist visas for those coming from China, which the Chinese foreign ministry called "unacceptable" and "unscientific".
Reacting to China's latest move, South Korea's foreign ministry told the BBC that its policy towards arrivals from China was "in accordance with scientific and objective evidence".
Japan meanwhile is currently allowing Chinese visitors into the country - provided they test negative for Covid.
According to South Korea's Disease Control and Prevention Agency, around a third of all arrivals from China tested positive for Covid prior to the visa restrictions being put in place.
At Seoul's Incheon International airport - the only South Korean airport still allowing flights from China - arrivals are met by military personnel in personal protective equipment.
The BBC managed to speak to some of them as they were escorted to the airport testing centre.
"Personally, I think it's OK. I have been through much worse during this pandemic," said William, a businessman from Shanghai. "As a traveller I just try to comply with the policies are much as possible."
But another passenger disagreed.
"In my mind it's not scientific at all," said Emily, who arrived from Hong Kong. She, like those coming from mainland China, was required to test.
"I feel like it's a little bit unfair on this side. They must feel really unsafe, I suppose."
Many South Koreans support the idea of protecting their country from China's coronavirus surge - but not all are convinced that the decision is a purely medical one.
"There is a political element to it and the relationship between the two countries isn't a good one. A lot of Korean people hold a lot of animosity blaming China for the coronavirus," said Jinsun, who was heading to Abu Dhabi.
Another woman going on her honeymoon to Paris said South Korea might not have implemented such rules if the country concerned wasn't China.
"But then again, whatever we did, China would have a problem with it," she said.
The South Korean curbs are supposed to last at least until the end of the month, which would give scientists time to analyse for any potential new variants coming from China.
"There's no transparency at the moment in China about any monitoring for new variants. If a new variant comes from China, it would be a very difficult situation for the whole world," Professor Kim Woo Joo, an infectious diseases expert at Korea University and a government adviser, told the BBC.
"It would also be a disaster for the Korean healthcare system. We currently have a lot of hospitalisations and deaths already and our elderly people are also under-vaccinated. This is what we are worried about."
At the moment, only a small number of business or diplomatic travellers from China are being allowed into South Korea. They must test negative before departure and also on arrival.
One Chinese man who tested positive escaped from a bus taking him to a quarantine hotel near the airport. Two days later he was caught by police in a hotel in Seoul.
Source: BBC