Russia has granted North Korean and Ukrainian boats permission to fish for saury in waters around Russian-held islands off Hokkaido that are also claimed by Japan, the Foreign Ministry said Wednesday.
The move comes despite Tokyo's assertion that the area is within its exclusive economic zone, the ministry said.
According to Press Secretary Norio Hattori, the ministry confirmed on July 26 that Russia had awarded North Korean fishing boats an 8,000-ton catch quota.
Hattori told a news conference that Russia had also put saury fishing rights out to tender on July 13 in Moscow. A Ukrainian firm won the bidding to the rights but Hattori said the firm's quota has not been confirmed by the ministry.
Hattori denied media reports that Taiwanese fishing boats are preparing to fish for saury in the area through an arrangement with the Ukrainian firm.
"We have not heard about it," he said.
The ministry lodged a protest Thursday via the Japanese Embassy in Moscow, complaining that the fishing accords violate Japan's sovereignty over the islands.
Although Japan has urged the Ukraine to refrain from fishing in the area, it has not lodged a protest with North Korea as Japan has no diplomatic ties with Pyongyang.
"We have restrictions with regards to North Korea," Hattori said. "But we will take appropriate action as we see the developments."
The latest revelations follow Japan's failure to stop South Korean vessels from catching saury in the disputed waters.
South Korean boats began fishing in the area last week despite repeated efforts by the Japanese government.
Tokyo has lodged protests with both Moscow and Seoul over the issue.
The new fishing accords are "very regrettable," Hattori said.