Last Thursday, Russian customs officers detained four Japanese fishing vessels for poaching near the South Kuril Islands, a former Japanese territory, off Russia's Pacific Coast.
The captains of the four trawlers refused to undergo a check and attempted to flee the scene.
A criminal case has been launched against Shigemi Fujimoto, 60, captain of one of the trawlers. The captain failed to produce permission to cross the Russian-Japanese border, while his fishing boat had no license to fish in Russian territorial waters.
Fujimoto said he had undergone no customs check and was asleep when the trawler crossed the border. Japan considers the waters concerned to be Japanese territory.
His vessel remains in the custody of authorities on the Russian island of Shikotan. Fujimoto himself was transferred to Japan on Thursday.
According to Tsubasa Maru, a Hokkaido-based fisheries association and the owner of the four boats, Fujimoto's trawler entered Russian waters after the captain had fallen ill. The other three boats followed Fujimoto's trawler across the border.
"If Japan fails to take effective measures, rather than mere words, to prevent any violations of the [1998 fishing] agreement in the immediate future, Russia reserves the right to raise the issue of future fishing in the area for Japanese fishermen," the Russian Foreign Ministry said in a statement on Thursday.
Confrontations over poaching between Russian authorities and Japanese fishing vessels are frequent in Russia's Pacific waters. Last August, a Japanese fisherman was shot dead near the Kuril Islands when Russian border guards opened fire at his boat after it refused to stop.
Russia and Japan have contested the ownership of the Kuril Islands for over 60 years, a dispute that has kept the two countries from signing a formal peace treaty after World War II.
