A Chinese military ship entered the waters of south-western Japan on Wednesday, EFE news reported quoting government officials.
This is the first such incident in over a decade and comes a week after a Chinese navy ship sailed near the disputed Senkaku islands.
Ap reported Deputy Chief Cabinet Secretary Hiroshige Seko as saying that a Maritime Self-Defense Force plane spotted the ship in Japanese waters west of Kuchinoerabu island in southern Japan before dawn. The ship sailed out of Japan's waters about 90 minutes later.
“The government will continue to take all possible measures for warning and surveillance activity for our territorial waters and airspace,” Seko said.
Japanese public broadcaster NHK reported it was the first time a Chinese naval vessel had been spotted in Japan's waters since a submarine was detected off Ishigaki island in 2004.
According to a Reuters report, the Chinese observation ship shadowed the powerful U.S. aircraft carrier, John C. Stennis, in the Western Pacific on Wednesday, a Japanese official said.
The show of American naval power comes as Japan and the United States worry Beijing will look to extend its influence into the Western Pacific with submarines and surface vessels as it pushes its territorial claims in the neighboring South China Sea.
Beijing views access to the Pacific as vital both as a supply line to the rest of the world's oceans and for the projection of its naval power.
Although incursions by Chinese coast guard ships in waters near Senkaku are common, this was the first time a navy ship did so.