The note of protest was sent to the Russian Foreign Ministry through the Japanese Embassy to Moscow on August 3, according to Suga.
Last Week, Japanese Defense Minister Itsunori Onodera called on Moscow at the 2+2 talks to take measures in relation to alleged military build-up in the southern Kuril Islands to avoid incidents and tensions.
"We have asked the Russian side to take certain measures in connection with the fact that Russia is boosting its military presence on the four disputed islands, with Russian military equipment being also very active [in the area]. Russia is our important neighbor, and we hope that maintenance of dialogue and cooperation will prevent ad hoc situations and unnecessary tensions," the Japanese minister explained.