South Korean fighter jets were scrambled after five Chinese military planes entered the country's airspace.
The Chinese aircraft entered the Korean Air Defence Identification Zone (KADIZ) from southwest of Socotra Rock.
The submerged rock is the subject of a maritime dispute between South Korea and China, and it serves as the foundation for a South Korean research station.
The KADIZ over the island overlaps with China and Japan's air defence zones.
China's planes stayed in the KADIZ for around two hours and 40 minutes, South Korea's Joint Chiefs of Staff said, according to a Yonhap report.
It added: "Our military confirmed that they are military planes of China through the Air Force's Master Control and Reporting Centre."
It also said the South's fighters took "normal tactical measures" until the Chinese planes left the zone.
A spokesman for the Joint Chiefs of Staff told Yonhap the Chinese planes included two bombers, two fighter jets and a reconnaissance plane.
"We talked with the Chinese side over a hotline and it said the operation was part of a routine exercise," he added.
"We are analysing its exact intention.".
It comes after South Korea said it was imposing a new round of economic sanctions on North Korea, whose sole major ally is China.
Recently, the deployment of a US missile defence system in South Korea has angered China, which fear's its powerful radar could look deep into the country and threaten its own security.
