Japan has complained to Russia after a coast guard patrol found a Russian vessel engaged in unauthorized activities in Japan's Exclusive Economic Zone.
Foreign Minister Fumio Kishida told reporters on Tuesday that patrollers found the vessel towing what looked like a cable off Cape Soya in Hokkaido, northern Japan, on Monday last week.
Kishida said ministry officials spoke with diplomats at the Russian Embassy in Tokyo to explain that scientific research or resource exploration inside Japan's EEZ is not allowed without prior consent or permission.
Kishida said members of the coast guard delivered a similar message to those on board the Russian vessel, and it subsequently left the waters.
He said patrols will continue to monitor developments in the country's surrounding seas.