TOKYO -- A Japanese submarine conducted a drill in the South China Sea alongside three other vessels, the Maritime Self-Defense Force said in a rare statement Monday as it aims to curb China's militarization of the region.
"Japan has been performing submarine exercises in the South China Sea since 15 years ago. We did so last year and the year before that," Prime Minister Shinzo Abe said on a TV program on Monday. "The purpose of the Self-Defense Force drills is to improve their skill. It is not intended for specific countries."
This is the first time that the MSDF has revealed exercises by a submarine in the South China Sea. On Thursday, the Hiroshima-based submarine Kuroshio joined helicopter carrier Kaga and two other destroyers for the training. The surface ships had been on a months-long assignment in the Southeast Asian region.
At the training, the three surface ships worked with helicopters to detect the submarine using sonars, while the Kuroshio pursued the carrier as it concealed itself.
The drills took place within China's self-declared maritime claim known as the Nine-Dash Line, which covers most of the South China Sea. Foreign Ministry spokesman Geng Shuang warned in a press conference Monday that outside countries should act carefully to maintain peace and stability in the region. The ministry probably avoided a stronger statement in consideration of Abe's planned visit to China in October.
After finishing the exercises, the Kuroshio's crew of roughly 80 made a port call to Cam Ranh Bay Monday to visit their Vietnamese counterparts. Vietnam also opposes China's ambitions in the region.
China is strengthening its presence in the South China Sea by building airstrips on artificial islands in the Spratly Islands and placing surface-to-air missiles on the Paracel Islands. Both archipelagoes are claimed by multiple countries.
Japan is expanding security cooperation with countries in the South China Sea to curb China's activity in the region.
The Kaga and two accompanying destroyers were deployed to the sea and to the Indian Ocean at the end of August. The vessels performed joint drills with the USS Ronald Reagan nuclear-powered aircraft carrier on Aug. 31 and the Filipino navy on Sept. 7. They will also stop in other countries like Indonesia and Singapore.
The U.S. takes issue with China's militarization of the South China Sea and is carrying out what it calls "freedom of navigation operations" there to deter such activity. It also disinvited China from this year's multinational Rim of the Pacific naval exercises.
Nikkei staff writer Oki Nagai in Beijing contributed to this report.