Japan's Navy Takanami class destroyers along the strait near Changi Naval Base in Singapore on May 15, 2017.

Japan is examining how to evacuate its roughly 60,000 citizens from South Korea in the event of a crisis that closes airports, with military ships being used as shuttles, a Japanese newspaper reported on Tuesday.

North Korea's pursuit of its military and nuclear programs in defiance of U.N. Security Council and other sanctions escalated tensions on the Korean Peninsula in 2017, which have only eased in recent weeks.

Working on the scenario of a crisis that shuts South Korean airports, the Japanese government has begun to look into plans for evacuations through the southern port city of Busan, the Yomiuri daily said, quoting multiple government sources.

Japanese and U.S. military vessels would take Japanese and U.S. citizens from Busan to Japan's Tsushima island, roughly 50 km (30 miles) from Busan, before ferrying them to the southernmost main island of Kyushu a day or so later.

Government officials have already visited Tsushima to inspect hotels and other potential lodging facilities, as well as planning for stocks of food and water, the paper added.

Japanese Chief Cabinet Secretary Yoshihide Suga told a news conference on Tuesday that the government is always considering various scenarios and making plans for its citizens' safety, but declined to give details, citing security concerns.

"It's a totally natural duty as a nation to use every means at our disposal for the protection and evacuation of our citizens if they should face danger abroad," he added.