The South previously announced military exercises for this week . NEW : Russian Foreign Ministry urges United States and South Korea to call off military drill . The U.S. is planning a massive joint exercise with the South Korean army in late April that will involve tens of thousands of troops from both countries. North Korea says it will deliver a `` self-defensive blow '' to the South if military exercise takes place . Yeonpyeong Island is a flashpoint between the Koreas .
NEW : Russian Foreign Ministry urges United States and South Korea to call off military drill . The U.S. is planning a massive joint exercise with the South Korean army in late April that will involve tens of thousands of troops from both countries. North Korea says it will deliver a `` self-defensive blow '' to the South if military exercise takes place . Yeonpyeong Island is a flashpoint between the Koreas .