Japan on Tuesday communicated to China its "interest" in a drone flight near the Senkaku Islands in the East China Sea the previous day, a senior Foreign Ministry official said, effectively calling on China to curb similar flights.
Defense Minister Itsunori Onodera meanwhile told reporters the ministry has strengthened daily monitoring by the Self-Defense Forces in the area, and that the SDF will maintain this posture as Wednesday marks the first anniversary of the purchase by the Japanese government of most of the islets last September.
The ministry conveyed its interest in the incident to the Chinese Embassy in Tokyo on Monday as the drone flew within Japan's air defense identification zone, an area where airplanes need to identify themselves and provide flight routes and other information.
Another senior ministry official said that while Monday's flight did not violate international law, Tokyo needs to remain vigilant about similar maneuvers.
Also Tuesday, seven Chinese Coast Guard vessels were spotted sailing in a contiguous zone just outside what Japan considers its territorial waters around the Senkaku Islands, according to the Japan Coast Guard.
An airplane believed to be a drone flew near the disputed islands on Monday morning, prompting the Air Self-Defense Force to scramble fighter jets. In the evening, China's defense ministry effectively admitted in a statement that the aircraft was a drone belonging to the People's Liberation Army.
The Senkaku Islands are at the heart of Japan's frayed ties with China, which claims the uninhabited islets it calls Diaoyu. The purchase by the central government from a private owner on Sept. 11, 2012, sparked widespread demonstrations in China and sent Japan-China relations to their lowest point in years.