Russian emergencies minister Yevgeny Zinichev on Wednesday visited an island claimed by Japan off Hokkaido that is at the center of a long-standing territorial dispute between the two countries.
It is the first visit to one of the four disputed islands by a senior Russian government official since August last year, when then Prime Minister Dmitry Medvedev traveled to Etorofu Island, known as Iturup in Russia, according to a Japanese government official.
Zinichev's trip to Kunashiri Island, called Kunashir by Russia, prompted an immediate reaction from Japan.
"(The visit) conflicts with our country's position, and we will deal with it properly after confirming facts," the Japanese Foreign Ministry said.
His trip was to attend a ceremony to open an emergency rescue center, according to Russia's Ministry of Civil Defense, Emergencies and Eliminations of Consequences of Natural Disasters.
The disputed islands collectively called the Northern Territories in Japan and the Southern Kurils in Russia, also include Shikotan and the Habomai islet chain.
The dispute has prevented the two countries from signing a postwar peace treaty.
The Soviet Union seized the islands following Japan's surrender in World War II in 1945, saying it acquired them as a legitimate outcome of the war. Tokyo says their seizure was illegal.
The emergency rescue center on Kunashiri Island is equipped with systems for monitoring and forecasting weather, and they are aimed at strengthening "the protection of the population and territory from natural and man-made emergencies," according to the Russian ministry.
It also said that a similar facility on Etorofu Island will start operating in the near future.