March 25 (UPI) -- South Korea scrambled fighter jets on Wednesday after a Chinese military aircraft trespassed into the Korean Air Defense Identification Zone, or KADIZ, according to Seoul's joint chiefs of staff.
The Chinese Y-9 surveillance aircraft strayed into South Korea-claimed airspace for 35 minutes without submitting prior notification, South Korean news service News 1 reported.
Air defense zones are unofficial airspace that does not overlap with territorial airspace. The Chinese aircraft did not enter South Korean territorial airspace, according to the report.
The Y-9 was first detected west of the Korean Peninsula at 9:35 a.m., in an overlapping area between KADIZ and Japan's Air Defense Identification Zone, or JADIZ.
At 12:36 p.m., it flew in a direction east of the South Korean city of Pohang.
The aircraft then entered an area of KADIZ at 10:06 a.m. southeast of South Korea's Jeju Island, leaving the area 17 minutes later through a KADIZ-JADIZ overlapping zone, Seoul said, according to Yonhap.
About 90 minutes later, the plane re-entered the KADIZ and remained in the zone for about 18 minutes.
South Korea's joint chiefs of staff said the military used a direct communication line with Chinese counterparts to request information regarding the flight.
On Wednesday the Chinese said the deployment was "normal military operations," South Korean news service Newsis reported. In response, the South Koreans deployed fighter jets to monitor the Y-9 surveillance aircraft, according to reports.
China has previously deployed aircraft in Korea's air defense zone without prior warning.
In 2019, South Korea said three Russian military planes and two Chinese warplanes entered its air defense identification zone without preliminary notification.
South Korean jets fired 360 rounds of warning shots at the time.