The Japanese Defense Ministry announced on September 18 that China's Liaoning aircraft carrier, escorted by two Luyang II-class destroyers, had been moving south through the waters between the islands of Yonaguni and Iriomote (Okinawa Prefecture, Japan) from September 17-18, according to AFP.

PHOTO: AFP/JAPAN MINISTRY OF DEFENSE

This is the first time a Chinese aircraft carrier has been confirmed to have passed through the area, Japan's Defense Ministry said.

Japanese Deputy Chief Cabinet Secretary Hiroshi Moriya said Tokyo had expressed serious concerns to Beijing, describing the incident as "completely unacceptable from the perspective of the security environment of Japan and the region".

NHK reported that the aircraft carrier had entered the contiguous zone, an area 12 nautical miles from the outer limit of territorial waters. Under international law, foreign ships are allowed to pass through the contiguous zone, but coastal states can take certain measures to prevent unauthorized activities.

Japan's Defense Ministry said it was monitoring the Liaoning and analyzing the purpose of the Chinese aircraft carrier's move.

In response, Chinese Foreign Ministry spokesman Lin Jian said that "relevant activities of the Chinese side comply with domestic and international laws."

Earlier, Taiwan's Defense Ministry announced that it had detected the group of ships moving through the waters east of the island towards Yonaguni Island, about 110 km east of Taiwan. Taiwan said it had detected them and sent forces to monitor them.

In August, Japan protested after a Chinese spy plane and a survey ship allegedly violated Tokyo's airspace and territorial waters.

Commenting on each incident, China's Foreign Ministry said the ship was only exercising its legitimate right of passage and asserted that it had no intention of violating any country's airspace.