The submarine Kuroshio docked at Vietnam's strategically important port of Cam Ranh Bay in Khanh Hoa province on Monday for a four-day visit. The Japanese Maritime Self Defense Force vessel, which measures 82 meters in length, is carrying a crew of 80. The visit is part of activities to celebrate the establishment of the Vietnam-Japan diplomatic relationship and to roll out agreements of the two nations’ defense ministries.

War ships of many countries have visited this ports as Vietnam seeks closer military ties with other countries in addition to China amid an unresolved maritime dispute in the South China Sea, to which Vietnam refers as East Sea.

Two MSDF destroyers made a port call there last year to take part in US-led joint drills.

The Kuroshio’s crew will play games, hold professional exchanges with Vietnam’s Region IV Naval Command, which is in charge of protecting the Spratly Islands, and make a trip to the resort town of Nha Trang, also in Khanh Hoa province.

The port call by the Kuroshio took place after it became the first Japanese submarine to take part in a naval drill in the South China Sea, according to Reuters. The exercise, conducted with other Japanese warships, is seen as an expansion of Japanese activity in the disputed waterway, which is essential to Japan’s sea-borne trade.

With the groundless imaginary nine-dash line, China claims virtually the entire area, including waters close to Brunei, Malaysia, the Philippines and Vietnam.