A South Korean Drone Unit is shown in an undated file photo unrelated to Thursday’s incident near the inter-Korean border. Photo by JEON HEON-KYUN / EPA

July 30 (Asia Today) -- Residents near South Korea's border with North Korea were briefly ordered to evacuate Thursday after the military detected an unidentified aircraft that was later confirmed to be a U.S. drone involved in a training exercise.

South Korean troops detected the aircraft south of a general outpost in northern Gyeonggi province and responded in accordance with established operational procedures, the Joint Chiefs of Staff said.

"After checking, it was confirmed to be a U.S. drone participating in training," a Joint Chiefs official said.

The aircraft was detected by South Korean personnel using thermal observation equipment. The military initially could not determine whether it belonged to South Korea, North Korea or another operator.