Former Russian President and Prime Minister Dmitry Medvedev said on Tuesday that the Japanese were “upset” because the Kuril Islands belong to Russia and could commit seppuku, but Moscow did not rule out a formal peace treaty with the island nation, Reuters reported.

The sharp comments by Medvedev, now vice president of the Security Council in Moscow, are likely to anger the Japanese government, which claims the 4 Kuril Islands, located in the south of the archipelago of 56 volcanic islands.

Japan calls these islands the “Northern Territories” because they were occupied by the Soviet Union in the final days of World War II. After the war, Moscow and Tokyo never signed a peace treaty, only an armistice.

On Tuesday, Medvedev said he was reacting to comments made by Japanese Prime Minister Fumio Kishida, who he said was in favor of a peace treaty with Russia.

“No one is against a peace treaty, with the understanding that the ‘territorial issue’ is closed once and for all in accordance with the Russian Constitution,” Medvedev said on his “X” account, formerly called Twitter.

In 2020, the Russian constitution was amended to prohibit any cession of territory.

Dmitry Medvedev also told the Prime Minister of Japan to commit seppuku

A Russian official also said on Tuesday that Japan will have to accept that Russia plans to “develop” the Kuril Islands and install weapons systems there.

“We don’t care about the ‘feelings of the Japanese’ about the so-called ‘Northern Territories.’ These are not disputed territories, but Russia,” he added.

“And those samurai who feel particularly sad can end their lives in the traditional Japanese way, committing seppuku. If they dare, of course,” said Dmytro Medvedev.

Last January, Medvedev suggested that Japanese Prime Minister Fumio Kishida commit suicide by seppuku because of his “obedience” to the United States.

The vice president of Russia’s Security Council echoed that sentiment on Tuesday, saying Japan was pandering to the United States despite dropping atomic bombs on the cities of Hiroshima and Nagasaki in 1945.

Where does the dispute between Russia and Japan come from regarding the Kuril Islands?

Tensions between Moscow and Tokyo have risen to unprecedented levels in the decade since the invasion of Ukraine began, as Japan has largely joined Western sanctions against Russia.

The Soviet Union occupied the Kuril Islands in the final days of World War II after launching a large-scale military offensive against Japan, which some historians believe contributed at least as much to Emperor Hirohito’s decision to order the surrender as the dropping of nuclear bombs on the cities. Hiroshima and Nagasaki by the United States.

Moscow and Tokyo never signed a peace treaty after the end of World War II, as the Russian invasion took place despite a military non-aggression pact signed between the two sides in 1941.

In 1951, Japan relinquished sovereignty over some of the islands under the Treaty of San Francisco, but states that this never included the islands of Itorofu, Kunasiri, Shikotan and Habomai in the south of the archipelago.

While campaigning for the presidential election in March, President Vladimir Putin said earlier in January that he would definitely visit the Kuril Islands “someday” and that tourism should be developed there.