Two Chinese military planes recently entered the overlapping air defense identification zone of South Korea and China, prompting South Korea to ready a sortie of fighter jets, the Joint Chiefs of Staff said Tuesday.

The Chinese jets entered the zone near Jeju Island on Sunday and flew out of it after South Korea sent a warning message, according to JCS spokesman Jeon Ha-kyu.

"We took necessary surveillance and tactical measures adequately," he said.

The ministry put fighter jets on standby in case the Chinese planes intruded into South Korean territory, he added.

The incident occurred amid a burgeoning stand-off between the Northeast Asian neighbors over the possibility that Seoul will introduce the advanced U.S. Terminal High Altitude Area Defense system.

The Pentagon wants to deploy the THAAD unit on the peninsula, citing North Korea's growing nuclear and missile threats.

But China is fiercely opposed to the plan, saying it is apparently aimed at curbing China's military influence.

In 2013, South Korea expanded its own air defense identification zone, called KADIZ, to cover Ieodo, a submerged rock. 

South Korea has scientific research facilities on Ieodo, which China also includes in its air defense identification zone. (Yonhap)