Japanese officials criticiszed Russia on Monday for its plans to lay fiber-optic cables to islands disputed by Tokyo and Moscow, calling the construction work "deplorable" and "without legal basis."
Ties between Japan and Russia have been strained for decades over the four islands, which were occupied by the Soviet Union in the closing days of World War II but are claimed by Tokyo.
They are known in Japan as the Northern Territories and in Russia as the Southern Kurils.
"It is extremely deplorable that such a project is being carried out under the Russian occupation that has no legal basis," government spokesman Yoshihide Suga told reporters
The Sankei Shimbun newspaper reported over the weekend that Russia plans to lay the cables between the disputed islands and Russia's Pacific island of Sakhalin.
The newspaper said Moscow had notified Tokyo of the project, which will be implemented by Chinese company Huawei Technologies.
"We've lodged protests via diplomatic routes with Russia and China," Suga said, adding that Japan "will patiently negotiate with Russia."
The dispute over the islands has prevented the two countries from signing a peace treaty to formally end wartime hostilities.
A visit by Japanese Prime Minister Shinzo Abe to Russia last month yielded no movement on the issue.
Strategically, control of the islands ensures Russia has year-round access to the Pacific Ocean for its Pacific Fleet of warships and submarines based in Vladivostok, through a strait that does not freeze over in winter.
© 2018 AFP