The Soviet Union seized the strategically located volcanic archipelago north of Japan’s Hokkaido in the final days of World War II and has maintained a military presence there ever since.

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 Soviet Union seized the strategically located volcanic archipelago north of Japan’s Hokkaido in the final days of World War II and has maintained 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 1988 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 official added.

A Russian court ordered the fishermen to pay an 11 million yen ($100,000) fine, Public broadcaster NHK reported.

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.

Agence France-Presse