Russian patrol planes have flown over the Sea of Japan where a Japanese Aegis destroyer has been deployed ahead of North Korea's planned rocket launch.
Japan's Defense Ministry said on Tuesday that 2 Russian IL-38 patrol planes were detected flying off the coast of the Sanin district.
The Russian aircraft were chased by Japanese fighter jets and changed their flight course to an area off the Noto Peninsula and the Tohoku region.
The Aegis destroyer, "Myoko", has been deployed In the Sea of Japan to prepare for the North Korean launch.
The Russian planes are believed to be gathering military intelligence on the Aegis air-defense system and the movements of Japan's Self-Defense Forces.
Russian patrol aircraft have repeatedly made similar flights over the Sea of Japan since late March to carry out reconnaissance missions.