North Korea is threatening South Korean civilian planes flying near its airspace amid heightened tensions on the divided peninsula. The Committee for the Peaceful Reunification of the Fatherland issued the threat Thursday, claiming upcoming joint US-South Korean military exercises were preparations for invading the communist nation. The statement said the North could not "guarantee the safety of South Korean civilian planes passing near our airspace." Washington and Seoul have repeatedly said the annual exercises are purely defensive. The joint drills begin next Monday. Tensions are particularly high in the region amid speculation the North is preparing to test-fire a missile.