South Korea has lodged a formal protest over a Chinese plane’s violation of the country's air defense identification zone(KADIZ).

According to Seoul’s Ministry of National Defense, Park Chul-kyun, deputy director general for international policy, summoned a defense official from the Chinese Embassy in Seoul on Monday to protest the military plane’s unauthorized entry into the KADIZ early in the day. 

Park told the official that Chinese aircraft have entered the zone six times this year alone, without advance notice, and that Seoul is taking the issue very seriously. He also urged Beijing to realize the gravity of such an incident and produce measures to prevent a recurrence. 

South Korea’s Joint Chiefs of Staff(JCS) revealed the Chinese plane, believed to be a Y-9 reconnaissance aircraft, entered the zone three times in the day, including from an area northwest of Jeju Island.