The foreign ministry has summoned China's ambassador to South Korea to lodge a complaint after a Chinese military aircraft intruded upon the South Korean air defense identification zone a day earlier, a foreign ministry official said Wednesday.

On Tuesday morning, the Chinese jet entered the KADIZ and approached 30 nautical miles, or 55.5 kilometers, northwest of Ulleung Island in the East Sea before flying out of the zone. The jet remained within the KADIZ for more than four hours before retreating when the South Korean military sent a warning message.

The jet was believed to be a reconnaissance plane. It was unprecedented for China's military aircraft to fly so close to South Korea's eastern airspace without Seoul's authorization.

"On Tuesday evening, First Vice Foreign Minister (Lim Sung-nam) summoned the Chinese ambassador to South Korea, (Qiu Guohong), expressed dissatisfaction and urged (him) to prevent a repeat of it," the ministry official stated.

"The Ministry of Foreign Affairs is working with the defense ministry to share info on the Chinese military aircraft's KADIZ entry and respond to it in a prompt manner," the official said.

Also on Tuesday, the Ministry of National Defense called in three Chinese military attaches based in South Korea and demanded that the incident not be repeated in the future. (Yonhap)