Japan's Defense Ministry said a strange submarine on June 18 appeared in the contiguous zone of northeastern Amami Oshima island of the country.

Destroyers and patrol aircraft of the Japan Maritime Self-Defense Force (MSDF) have been deployed to track submarines.

This is thought to be a submarine of the Chinese navy, but Japan's Defense Ministry declined to disclose this as well as the submarine model as it could reveal clues about the detection capability of the MSDF.

Under international law, submarines must rise and raise their flags when entering another country's territorial waters.

The area adjacent to the territorial sea is the sea area outside the territorial sea and adjacent to the territorial sea, with a width not exceeding 24 nautical miles from the baseline used to calculate the width of the territorial sea.

The MSDF patrol track was used to track and track strange submarines from Kanoya base in Kagoshima and Naha base in Okinawa and Ashigara Aegis from Sasebo base in Nagasaki and helicopters.

Foreign submarines "may want to test US and Japanese anti-submarine warfare capabilities," a source from the Japan Self-Defense Force (SDF) said.

In January 2018, Japan announced the discovery of a Chinese nuclear-powered submarine near the Diaoyu / Senkaku Islands.