Japan detected a submarine believed to be Chinese off a southern Japanese island, the defense ministry said Sunday, heightening Japan’s caution levels in the East China Sea as China increases its military activities.
The submarine remained submerged, but the ministry said in a statement that it believes the submarine is Chinese because a Chinese Luyang III-class guided missile destroyer is near the submarine.
The submarine moved northwest off the eastern coast of the Amamioshima Island, about 700 kilometers (420 miles) northeast of the disputed East China Sea islands controlled by Japan but also claimed by Beijing, the ministry said.
The submarine on Sunday morning was heading west in the East China Sea.
Neither the submarine or the ship entered Japanese territorial water. Under international law, submarines passing off the coast of another country are required to surface and show a national flag inside territorial waters.
Japan’s Maritime Self-Defense Force sent three reconnaissance aircraft and two destroyers to the area for early warning and information gathering to analyze China’s intentions.