A helicopter of China's State Oceanic Administration approached a Maritime Self-Defense Force destroyer Monday afternoon near an East China Sea gas field where both Japan and China have claimed exploration rights, according to the Defense Ministry.
The government lodged a protest with China through diplomatic channels, calling the helicopter's approach a "dangerous act."
The incident occurred at around 1:25 p.m. where China is developing a gas field called Shirakaba in Japan and Chunxiao in China, with the helicopter approaching as close as 70 meters to the vessel horizontally and only 40 meters above the sea, the Defense Ministry's Joint Staff said.
The helicopter circled the area where the destroyer Samidare was on a monitoring mission before flying off toward the west, it said.
The gas field is located near what Tokyo claims is the median line between the exclusive economic zones of Japan and China.
There were two cases last April in which a Chinese naval helicopter came as close as 90 meters to an MSDF destroyer.