In the latest indicator of their stronger defense relations, the Japanese and US navy held their first-ever cooperative anti-submarine practice in the South China Sea.

Two of Japan's destroyers, the JS Kaga and JS Murasame, as well as an Oyashio-class submarine, joined an American Aegis destroyer, the USS Milius, for the exercise on Tuesday, which also included Japanese SH-60J helicopters and US and Japanese patrol aircraft.

Last week, the three destroyers took part in another drill in the South China Sea, and the Japanese ships also made a weekend port call in the Philippines before joining the Philippine frigate BRP Jose Rizal for an exercise off the coast of Subic.