According to several media reports, South Korea scrambled fighter jets to intercept a Chinese military aircraft that entered the South’s air defense zone, called the KADIZ.

“The aircraft entered the country’s air defense identification zone, called the KADIZ, at around 8:03 a.m. near Ieo Island and exited at 8:27 a.m.”, the South Korean Joint Chiefs of Staff said in a statement.

The Chinese aircraft was believed to be a military reconnaissance plane.

“It re-entered the KADIZ at 9:34 a.m. near the southeastern city of Pohang, and flew between Ulleung and the easternmost islets of Dokdo, eventually leaving the air defense zone at 12:51 p.m.” added in Joint Chiefs of Staff (JSC).

The Republic of Korea Air Force deployed fighter jets to counter a Chinese military plane flying in the country’s air defense domain without notice and sent a warning message, the JSC said.

South Korea’s defense and foreign ministries plan to lodge a protest against China for entering the KADIZ without notice later in the day.

A section of the KADIZ overlaps with the air defense zones designated by China and Japan, a source of potential tension among the regional powers, according to Yonhap.

The zone was established in 1951, during the Korean War, by the United States Air Force to block communist forces. In 2013, in response to the establishment of a Chinese zone that covers disputed territory, the South Korean government considered expanding their zone to include islands of Marado and Hongdo, and Ieodo, a submerged rock within the overlapping exclusive economic zones of South Korea and China.