The sister of Kim Jong-un, North Korea’s leader has warned of retaliatory measures against South Korea.<br />According to Reuters, Kim Yo Jong has said that the retaliatory measures could involve the military.<br />The tension between the two countries is focused on defectors from the North.<br />The defectors have reportedly been sending anti-north propaganda and rice to people in North Korea.<br />The defectors use balloons to sail the items overhead or place the items in bottles in the sea.<br />South Korea's Defense Ministry has said they are ready to respond to “all situations,” and are closely monitoring the North Korean military.