Photo/Illutration Crew members pose for a photo with the Japan Coast Guard survey vessel Heiyo in Shimonoseki, Yamaguchi Prefecture, in January. (Asahi Shimbun file photo)

Tokyo lodged a protest with Seoul after a South Korean coast guard vessel called on a Japan Coast Guard ship to halt a survey in waters off Nagasaki Prefecture on Aug. 15.

The Japan Coast Guard announced that day that the South Korean vessel radioed its 4,000-ton hydrographic survey vessel Heiyo around 4:20 a.m. to stop its work.

The Japanese ship was in waters 141 kilometers off Meshima, an islet in Goto, in the prefecture, at that time, which the Japan Coast Guard said was within Japan’s exclusive economic zone.

The South Korean government vessel’s calls for halting a survey marked the first time it has done so while a Japan Coast Guard survey ship was engaged in waters in the Japanese EEZ.

They came when the Japanese survey vessel was sailing about 10 km on the Japanese side from the median line from the shores of the two countries, according to the Japan Coast Guard.

The Heiyo crew replied to the South Korean vessel that it was conducting a “legitimate survey within Japan’s EEZ.”

The Japanese boat is continuing its oceanographic work.

As of the morning on Aug. 16, the South Korean vessel was repeating its calls for the suspension of the survey as it was sailing in parallel to the Japanese ship.

The Heiyo has been conducting the survey in this ocean area since Aug. 13.