TOKYO (Kyodo) — Japan’s Defense Ministry said Tuesday it decided to cancel a port call by a destroyer in South Korea this spring as relations between the two countries have been strained over alleged provocative acts by each of their militaries.

Several Maritime Self-Defense Force ships including the Izumo destroyer had been slated to call at Busan on their way to nearby waters where a multilateral exercise is to be held from April to May, when defense ministers from the Association of Southeast Asian Nations and its regional partners meet in the South Korean port city.

The Japanese ships will take part in the joint drill as planned, according to the ministry.

Tokyo is seeking to improve relations with Seoul, but this time judged it is “the most appropriate” not to have the ships arrive in South Korea, the ministry’s press secretary, Hajime Aoyagi, said at a press conference.

As for future interactions with the South Korean military, he said the ministry will “determine on a case-by-case basis.”

The two countries have been at odds over whether a South Korean navy destroyer locked its fire-control radar on the MSDF’s patrol aircraft in the Sea of Japan in December. The Japanese ministry concluded last month that South Korea’s denial is baseless and that it cannot continue bilateral defense talks on the incident.

South Korea, meanwhile, has claimed Japanese patrol planes repeatedly flew at a dangerously low altitude over South Korean warships in international waters in December and January. Japan has denied the allegation.

Last week, the South Korean Defense Ministry said it would postpone an official visit to Japan by the commander of the South Korean navy’s First Fleet originally scheduled for this month.

The situation added to increased bilateral tensions following recent rulings by South Korea’s top court that ordered Japanese firms to compensate for wartime labor.