Russia’s government has denied that two of its fighter jets breached Japanese airspace near Hokkaido.
However, Japan’s claim that Russia entered its airspace re-ignites a decades-long dispute between the two countries over islands that they both lay claim to.
The accusation came just hours after Japanese Prime Minister Shinzo Abe said he had “high hopes” of finally settling the row. He was speaking at an event to commemorate the Northern Territories on February 7.
Meanwhile, nationalist demonstrators gathered near the Russian embassy in Tokyo, shouting “Give us back our islands!”
Japan believes the disputed islands are part of their Northern Territories, but Russia calls them the Southern Kuril Islands.
They were occupied by Soviet forces at the end of World War II and became part of the USSR when the war ended.
Japan has always disputed the annexation, and the two countries are yet to sign a peace treaty – more than 65 years later.