SEOUL, South Korea (AP) — South Korea says its troops fired warning shots toward North Korea along their tense border in the first such incident since the rivals took unprecedented steps to lower front-line animosities. The military in Seoul says North Korean troops fired several bullets at a South Korean guard post inside the border zone early Sunday. South Korea responded with 20 warning shots. Violent confrontations have occasionally occurred along the border. The incident didn’t cause any known casualties on either side and observers say is unlikely to escalate. It comes two days after North Korean leader Kim Jong Un reappeared in public after a 20-day absence amid speculation about his health.