(RIA Novosti) – Japan placed its air force on alert on Friday after two Russian Tupolev Tu-95 Bear strategic bombers flew near its airspace, the Japanese military said.

The two Russian bombers reportedly flew near Japan’s northernmost Hokkaido island and flew above the Sea of Japan past the Honshu island.

The Russian aircraft did not violate the country’s airspace, but Japanese fighter jets were put on alert, the Japan Self-Defense Forces said.

Two similar incidents, involving Russia’s Tu-95 and Tupolev Tu-142 reconnaissance planes, were reported in November.

The Japan Air Self-Defense Force was put on alert 105 times between July and September because of flybys by Russian aircraft, according to military authorities.

Japan remains very sensitive to the Russian military activity near its borders as bilateral relations have long been overshadowed by a territorial dispute over the Kuril Islands in the north Pacific.

The four disputed islands – Iturup, Kunashir, Shikotan and Habomai – were occupied by Soviet forces at the end of World War II and are still claimed by Japan.

The two states never signed a permanent peace treaty following the end of World War II because of the row over the islands, which Russia calls the Southern Kurils and Japan calls the Northern Territories.