Russia on Thursday announced the suspension of a cooperation agreement for the decommissioning of its nuclear weapons signed with Japan in 1993, amid the deterioration of bilateral relations following Moscow's invasion of Ukraine in February 2022.

Russia disclosed an order signed Tuesday by Prime Minister Mikhail Mishustin stating that the Kremlin will notify Tokyo of the termination of the agreement that provides for Japanese support to decommission weapons, including dismantling nuclear submarines.

But the work has stalled as Moscow has refused to send related military data to Tokyo. The agreement was signed after the revelation in 1993 that Russia's Vladivostok-based Pacific fleet had dumped radioactive waste into the Sea of Japan.

Japanese Chief Cabinet Secretary Hirokazu Matsuno said at a news conference in Tokyo on Friday, "It is regrettable that the Russian government has unilaterally announced the suspension of the pact without notification in advance."

The move follows other unilateral steps by Russia, including the suspension of negotiations for a postwar peace treaty with Japan in March 2022, one month after Tokyo began imposing economic sanctions on Moscow in the wake of its aggression against Ukraine.

Russia has also withdrawn from joint economic activities on islands it controls that are claimed by Japan. The disputed islets off Hokkaido are known as the Northern Territories in Japan and the Southern Kurils in Russia.