South Korea says North Korean warplanes flew close to the nations’ dividing border Thursday, causing Seoul to scramble its own jets in response. The South Korean military said a formation of eight North Korean fighter jets and four bombers were believed to have been conducting air-to-surface firing drills. South Korea scrambled 30 of its own jets when the threat was spotted. The aerial standoff comes after Pyongyang fired two ballistic missiles toward its eastern waters Thursday. Seoul responded by carrying out drills alongside the U.S. and Japan off the peninsula’s east coast. Tension in the region has been steadily rising, with Kim Jong Un firing a nuclear-capable missile over Japan.