Russia’s top security agency says it has arrested four Russians accused of making preparations to kill senior Defense Ministry officials on Ukraine's orders.

Russia’s Federal Security Service said on Thursday it had foiled several plots by Ukrainian intelligence services to kill high-ranking Russian officers and their families in Moscow using bombs disguised as power banks or document folders.

Igor Kirillov, who was named the head of Russia’s nuclear defense forces in April 2017, was under sanctions from several countries including the U.K. and Canada for his role in Ukraine.