- Japan says a Chinese Navy survey ship sailed into its territorial waters on Saturday.
- The incident comes just days after a Chinese military spy plane flew into Japanese airspace.
- China asserted that the two incidents weren't linked, adding that the ship's passage was legal.
Japan accused China of sailing into its territorial waters just days after one of Beijing's spy planes violated Japanese airspace for the first time.
The incidents, which China asserted aren't linked, are sparking further tensions between the two nations.
Japan's Ministry of Defense confirmed the incursion on Saturday, detailing that at around 6 a.m., the Chinese Navy vessel moved eastward into territorial waters west of Kuchinoerabu Island, which is located in the Tokara Strait southwest of the country's four biggest islands.
The Chinese Schuppan-class survey ship remained in that area before departing southwest of Yakushima Island at around 7:53 a.m.
A map published by the defense ministry showed the movement of the Chinese vessel.
In response, Namazu Hiroyuki, director-general of the Japanese Foreign Ministry's Asian and Oceanian Affairs Bureau, said the ministry "issued Japan's strong concern and protest" to China's embassy in Tokyo, highlighting "past activities of Chinese naval vessels and others in the waters around Japan."
Hiroyuki also noted the recent violation of Japan's airspace by a Chinese military spy plane just last week.
Japan said a Chinese Y-9 intelligence-gathering plane briefly entered Japanese airspace near the Danjo Islands, located southeast of Nagasaki. The plane was in Japanese airspace for three minutes, and Japan's Air Self-Defense Force scrambled fighter jets in response.
Maps showed the plane's flight path. While it was the first reported Chinese airspace violation of Japan, Japan previously scrambled jets over 600 times between April 2023 and March 2024, mostly in response to Chinese military aircraft.
While the quick succession of both incidents raised concerns in Tokyo, China said they weren't linked.
Chinese Foreign Ministry spokesperson Mao Ning said Monday that the Tokara Strait "can be sured for international navigation, and by sailing through the strait, the Chinese vessel was exercising its right of transit passage, which is fully lawful and legitimate," citing the United Nations' international maritime laws.
She added that there was "no need to arbitrarily link or interpret" the two incidents.
China and Japan find themselves at a particularly sensitive moment in their relations as they attempt to work through critical issues, such as Japan's release of treated radioactive water from the Fukushima nuclear power plant last fall and Beijing's rising tensions with Taiwan.