Tensions have escalated between China and Japan after a plane, reportedly flown by Japanese ultra-nationalists, was seen over a contested island in the East China Sea, an area both countries have disputed for years. According to the Chinese coastguard, one of their patrols observed a Japanese civilian aircraft "illegally" entering the airspace of an island in the Diaoyu group, which Japan refers to as the Senkaku Islands, on Saturday morning. The plane reportedly exited the area within five minutes, after which a Chinese helicopter was dispatched to issue a warning and drive it away. 

On Sunday, the Chinese foreign ministry stated that the aircraft was operated by “ultranationalist activists,” and that Liu Jinsong, who leads the ministry’s Asian affairs department, had formally protested to the Japanese embassy. The ministry said Liu called on “the Japanese side to immediately stop illegal activities which violate China’s sovereign rights and take measures to prevent similar incidents.” Similarly, Wu Jianghao, China’s ambassador to Japan, issued a protest over what he called an “illegal intrusion,” saying it was a serious breach of China’s sovereignty and warning that Beijing would “resolutely take countermeasures” if there were any “new provocative moves.” At the same time, Tokyo filed a complaint with Beijing after spotting four Chinese coastguard vessels in what it claims are its "territorial waters" near the disputed islands. 

Tokyo stated that Vice-Minister for Foreign Affairs Takehiro Funakoshi had lodged a “strong protest” with Wu over the “intrusion” and “violation of Japan’s territorial airspace” by a helicopter launched from a Chinese coastguard vessel, and called on Beijing to prevent such incidents from happening again. According to Kyodo News, Japan's Self-Defence Forces shuffled two fighter jets after spotting the helicopter flying over the disputed islands. In response, China’s defence ministry criticised Japan’s remarks as “distorted and irresponsible”. It urged Japan “to strictly restrict the activities of its nationals and stop any provocative moves that … may affect the overall bilateral relationship”. 

The Diaoyu Islands, five small uninhabited islands and three reefs between Taiwan and Okinawa, are surrounded by waters rich in natural resources like fish, oil, and gas. The long-running dispute between China and Japan over control of these islands often resurfaces, straining their bilateral ties. In recent years, Chinese coastguard activity has increased in the area, with tensions escalating after they removed a buoy and forced out four Japanese fishing vessels in late March. According to Kyodo, Chinese ships have entered what Japan asserts as its territorial waters around the islands 11 times this year. They have been in those waters and Japan’s claimed contiguous zone for 166 consecutive days.