MOSCOW (Reuters) - Russia said on Monday it had built new barracks for troops on a disputed chain of islands near Japan and would build more facilities for armored vehicles, prompting a diplomatic protest from Tokyo.

Russia’s Ministry of Defence said it planned to shift troops next week into four housing complexes on two of the four disputed islands, known as the Southern Kurils in Russia and the Northern Territories in Japan.

Japan’s defense ministry says 3,500 Russian troops are deployed on the two larger islands as part of a military buildup.

The news came after the Kremlin said Japanese Prime Minister Shinzo Abe might visit Russia on Jan. 21 as the two countries step up efforts to defuse the territorial dispute that has prevented them from signing a World War Two peace treaty.

In Tokyo, Foreign Minister Taro Kono told a regular news conference that Japan would lodge a protest.

Japan said in July it had asked Russia to reduce its military activity on the islands, a plea Moscow dismissed as unhelpful megaphone diplomacy at the time.

“We plan to lodge a protest,” Kono told reporters, adding that Japan would clearly state its position during negotiations.

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“The premise of the upcoming negotiations is solving the island issue and concluding a peace treaty,” he said.

Soviet forces seized the four islands at the end of World War Two. Russia and Japan both claim sovereignty over them.

Despite the tension over the islands, the neighbors are discussing various other issues. At economic talks in Tokyo on Tuesday, the two sides said there was progress in areas such as energy and medicine, Kyodo news agency said.

MISSILES

Diplomats on both sides have spoken of the possibility of reviving a Soviet-era draft agreement that envisaged returning two of the four islands as part of a peace deal.

President Vladimir Putin and Abe have held numerous meetings to try to make progress on the issue.

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Japan says it is concerned by what it regards as an unhelpful Russian military build-up on the islands - which has included warplanes, missile defenses and other deployments.

Russia says it is perturbed by Japan’s roll-out of the Aegis Ashore U.S. missile system, part of Japan’s defense plans to counter China, North Korea and Russia.

Russian politicians say they fear Japan might agree to deploy U.S. missile facilities on the islands if any are returned to Tokyo, and that Moscow could only countenance a deal if it received a guarantee that ruled out such a scenario.

In the meantime, Moscow is fortifying the islands.

Russia’s Defence Ministry said on Monday it wanted troops and their families to move on Dec. 25 into two new housing sites on the island of Iturup (Etorofu in Japan), and into two other complexes on the island of Kunashir (Kunashiri in Japan).

Troops moved into two similar facilities last year and three more barracks are planned for 2019, the ministry said.

“Also on both islands we have modern and heated storage facilities for weapons and armored vehicles,” the ministry said in a statement, adding that more such facilities were planned.