The Chinese plane spent more than four hours in the Korea Air Defence Identification Zone (ADIZ) after flying near a submerged rock in the area controlled by Seoul but claimed by Beijing, the South Korean Joint Chiefs of Staff (JCS) said in a statement.

South Korea’s Air Force deployed more than one fighter jet to track and blare warnings to the Chinese aircraft to leave, the JCS said.

There was no immediate comment from China.

The ADIZs are not legally binding agreements under international treaties, but Seoul extended its own territory in 2013 to partially overlap with a zone newly declared by China.

China’s expansion included the submerged rock named Ieodo, which Seoul controls with a research station platform built atop it.

Chinese warplanes made a similar flight over the South Korean zone in February and April, the JCS said, while at least two similar instances were observed last year.

In February, Seoul summoned the Chinese ambassador to lodge a complaint, and Beijing said then the aircraft was in a training in line with international law and practice.