A Russian reconnaissance plane was found to have monitored how South Korea and Japan managed their missile defense systems at the time of a North Korean rocket launch earlier this month.

Japan’s Sankei Shimbun said Thursday that a Russian reconnaissance plane, the IL 20, reportedly gathered information on the radar frequencies used by South Korea and Japan and the roles Japan’s Self-Defense Forces were given as part of missile defense activities.

North Korea launched its Daepodong-Two rocket on April fifth in what Pyongyang says was an attempt to put a satellite into orbit as part of the peaceful development of its space program.