The Russian Navy’s Pacific Fleet has deployed state-of-the-art anti-ship missile systems on two of the islands off Hokkaido claimed by Japan, the fleet’s newspaper reported recently.

The Bastion missile system has been installed on Etorofu Island and the Bal system on Kunashiri Island, according to the report.

Russian Defense Minister Sergei Shoigu said in March his country would deploy the surface-to-surface missiles systems on the islands before the end of the year.

The row over the four Russian-held islands off Hokkaido has prevented the two countries from signing a peace treaty following World War II.

The report comes as Prime Minister Shinzo Abe said on Monday in Buenos Aires that signing the treaty will require a “relationship of trust” between himself and President Vladimir Putin.

A day earlier Putin poured cold water on Japanese hopes of quickly concluding a World War II peace treaty. Putin said such an agreement is “not an easy path,” reiterating that the contentious islands, seized from Japan by the Soviet Union at the end of World War II in 1945, fall under Russian sovereignty.

The islands — Etorofu, Kunashiri and Shikotan as well as the Habomai group of islets — were seized by the Soviet Union following Japan’s surrender in August 1945. The islands are called the Northern Territories in Japan and the Southern Kurils in Russia.

The deployment of Bastion missile-launchers to Etorofu appears to have come in tandem with a similar move in its tiny Kaliningrad exclave, which borders NATO members Poland and Lithuania, reports said Monday.

Elsewhere, a Russian Navy Kamov Ka-27 anti-submarine helicopter flew near the Senkaku Islands in the East China Sea on Tuesday, prompting Japan to scramble Air Self-Defense Force fighter jets.

The Self-Defense Forces’ Joint Staff said the helicopter came within about 10 kilometers of Japanese air space over the Kuba and Taisho islands, which are part of the Senkakus. Russian Navy vessels, including a missile destroyer, were also spotted in nearby waters.