Russian officials say they are set to impose fines on the crews of Japanese fishing boats seized on Tuesday. They were taken to one of four Russian-held islands claimed by Japan and inspected on suspicion of illegal fishing.
The five boats, based in Nemuro City, were taken to a port on Kunashiri Island. Twenty-four fishermen were on board.
Japanese officials say they were fishing for octopus under an agreement between Japan and Russia.
Japan's Foreign Ministry says the fishermen voluntarily allowed the Russian officials to search their vessels, as requested.
Russian border officials say they found about 6 tons of undeclared octopus catch. They told NHK they will consider the matter further and decide on a penalty.
Japan's top government spokesperson criticized the Russian action.
Chief Cabinet Secretary Yoshihide Suga said, " The seizure of Japanese fishing boats by Russia is unacceptable. The government has lodged a strong protest with Russia and has urged it to return the boats swiftly for humanitarian reasons."
The Japanese Consulate General in Yuzhno-Sakhalinsk say the crews of the boats are reportedly in good health.