File Photo: Boats on dry dock at the harbour outside the town of Kurilsk on the island of Iturup, in the Kuril Islands Photograph:( AFP )
The Kuril Islands were seized from Japan by the Soviet Union at the end of World War II and Russia continues to maintain a military presence in the region, despite vivid opposition from Tokyo.
Russia released 24 Japanese fishermen and their vessels on Tuesday, after detaining them for allegedly exceeding the octopus catch quota off a chain of disputed Pacific islands, Japan's foreign ministry said.
The five boats departed a port in Kunashiri island, one of the four southern Kuril islands disputed by Tokyo and Moscow, a foreign ministry official in charge of Russian affairs confirmed.
The fishermen are in good health, top government spokesman Yoshihide Suga later told reporters.
The Soviet Union seized the strategically located volcanic archipelago north of Japan's Hokkaido in the final days of World War II and Russia has continued to maintain a military presence there ever since.
The five ships were detained last week after a Russian inspection deemed they had exceeded their quota for octopus allowed under a 1998 agreement.
Foreign ministers discussed the incident at talks last Thursday, which also tried to find a breakthrough in the long-lagging dispute between Moscow and Tokyo over the islands.
Details about the Russian allegation "will be probed by relevant organisations", the Japanese ministry official added.
A Russian court ordered the fishermen to pay an 11 million yen ($100,000) fine, which was paid before leaving for Japan, sources said.
Russian President Vladimir Putin and Japanese Prime Minister Shinzo Abe have met more than two dozen times since 2013 over the territorial dispute, which prevented the two countries from signing a peace treaty to formally end World War II.
Tokyo maintains its claim over the four southernmost islands of the Kuril chain, known as the Northern Territories in Japan.
Nationalist sentiment on both sides makes both governments wary of considering concessions.