South Korea said on Friday it would suspend visas and visa waivers for Japan in response to Tokyo's own travel restrictions on Koreans, as fears over the spreading coronavirus rekindled a feud between the neighbours dating back to before World War Two.
South Korea's curbs, which will take effect on Monday, also include special entry procedures for non-Japanese foreigners arriving from Japan, Vice Foreign Minister Cho Sei-young told a briefing.
At present, Japanese can visit South Korea for 90 days without a visa and those already in the country will be allowed to stay for that period.
The Korean moves came just hours after Seoul summoned the Japanese envoy to protest against Japan's decision to quarantine South Korean visitors for two weeks.
Japan is among almost 100 countries to impose curbs on travellers from South Korea, which has suffered 44 deaths and 6,593 infections in the biggest outbreak outside China, where the virus emerged late last year.
The number of coronavirus cases in Japan stood at around 1,060 on Friday, with new infections reported from Yamaguchi prefecture in the southwest to Hokkaido in the north, according to national broadcaster NHK.
Japan has barred entry to visitors from highly affected areas in South Korea and ordered two weeks' quarantine for others.
"If the Japanese government does not withdraw their decision...we cannot help but devise necessary countermeasures, including reciprocal measures," South Korean Foreign Minister Kang Kyung-wha told Japanese Ambassador Koji Tomita earlier in the day.
"We express deep regret towards the unjust measures taken by the Japanese government."
Japanese Health Minister Katsunobu Kato told reporters in Tokyo that the quarantine instructions, which would also apply to visitors from China, would take the form of a request for them to stay in their hotels.
"We'll do everything to make sure people understand," he said.
Seoul has protested to Southeast Asian neighbours Singapore and Vietnam over similar curbs.
Tokyo faced "mistrust from the international community due to its opaque, passive" response to the virus outbreak, South Korea's National Security Council said after a meeting at the presidential Blue House earlier in the day.
The rapid spread of the disease has raised doubts about whether Tokyo will be able to host the Olympics this summer, but the government has insisted that the Games will go ahead as scheduled.
The number of new cases of the virus fell to 505 in South Korea on Friday, from 760 the previous day, the Korea Centers for Disease Control and Prevention (KCDC) said.
Vice Health Minister Kim Gang-lip said authorities had almost finished tests on more than 200,000 followers of a church in southeastern Daegu at the centre of the outbreak.
More than 90% of South Korea's infections were in Daegu and nearby North Gyeongsang province. Smaller clusters elsewhere include a new one reported on Friday at a hospital in Seongnam, southeast of the capital.
The number of South Korean visitors to Japan fell nearly 26% last year to 5.6 million, the first drop since Japan's tsunami and nuclear disaster in 2011, Japanese tourism officials say.
Difficult relations between Japan and South Korea date from the former's sometimes brutal occupation of the Korean peninsula from 1910 to 1945. Japan's use of Korean girls and women in military brothels during World War Two still prompts fury in South Korea.
Last year, Tokyo slapped trade curbs on South Korea, which responded with a boycott on Japanese goods and services.