A Chinese naval helicopter approached a Japanese research ship within the country's exclusive economic zone in the East China Sea, the Fisheries Agency has said.

The Japanese government told the Chinese government through a diplomatic channel that the incident on Friday was regrettable and Beijing should prevent any similar occurrences in the future, the agency said.

Coming from behind the Yoko Maru of the fisheries research and education agency, the helicopter reached a point roughly 150-200 meters from the vessel and more than 30 meters above the sea in waters northwest of Okinawa around 10:47 a.m. Friday before flying away, the Fisheries Agency said.

The Japanese ship was doing fisheries resource research in the EEZ, which extends some 370 kilometers from the Japanese coastline, at the time of the incident.

Each country can develop natural resources, build islands and apply domestic law regarding issues such as fisheries within its exclusive economic zone, which is defined under the U.N. Convention on the Law of the Sea.