Russian missile troops held drills on a disputed island which both Japan and Russia claim as their own, the Interfax news agency cited Russia's Defense Ministry as saying on Thursday.
Soviet troops took control of the four islands off Hokkaido - known in Russia as the Kurils and in Japan as the Northern Territories - at the end of World War II and they have remained in Moscow's hands since. The dispute has prevented the two countries from signing a peace treaty.
Interfax said on Thursday that Russian troops had practiced moving and camouflaging their vehicles on Matua island. Moscow said in May it would establish observation posts on the islands.
More recently, Russia has pushed back against a growing military alliance between the United States and Japan, which it has cast as a "stumbling block" to the signing of any peace agreement with Tokyo.
Kremlin spokesman Dmitry Peskov said earlier this week that evidence that Japan was increasingly aligned with what he called "the collective West" could only be "detrimental to our bilateral relations."
