(Bloomberg) -- Japan reinstated a reference to Russia’s “illegal occupation” of disputed islands in its annual diplomatic report for the first time in 19 years, as relations between the neighbors turn increasingly hostile following the Kremlin’s invasion of Ukraine. 

The two countries have been locked in a territorial dispute over a group of islands known as the southern Kurils in Russia and the Northern Territories in Japan for more than 75 years. The Soviet Union seized the disputed islands in the final days of World War II, expelling thousands of Japanese residents. 

“The Northern Territories are inherent territories of Japan that are currently under illegal occupation by Russia,” the ministry said in the report, which was published Friday on its website. The “inherent territories” wording had also been absent from the so-called blue book since 2011, the ministry said in an email. 

Japan had played down its claims over the past two decades, in an attempt to bolster ties with Russia and seal a peace treaty that would formally end hostilities. But since the Russian invasion of Ukraine, Japan has closely followed the U.S. line on sanctions, expelling Russian diplomats. Tokyo has also frozen the assets of about 500 individuals as well as organizations and financial institutions including Sberbank. 

Prime Minister Fumio Kishida has pledged to ban imports of Russian coal, though he hasn’t given any time line for achieving this. Japan also imports oil and gas from Russia. In response to Japan’s sanctions, Russia placed Japan on a list of “unfriendly” countries and ended talks on the islands, which former Russian President Dmitry Medvedev said were little more than a “ritual.”

The ministry also expressed strong concern about an increase in joint military activity involving Russia and China in the region surrounding Japan, public broadcaster NHK said.

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