Seoul threatened to retaliate Friday over what it called Tokyo's "irrational" plan to quarantine arrivals from
South Korea over the coronavirus outbreak, turning the scientific issue into a diplomatic row.
The two countries have close economic ties and are both major US allies, democracies and market economies faced with a rising
China and nuclear-armed North Korea.
Japanese Prime Minister
Shinzo Abe on Thursday announced that foreign arrivals who have recently been in China or South Korea would be required to spend 14 days in quarantine.