South Korea's military said it had scrambled fighter jets when Chinese and Russian military planes entered and left its air defence zone on Tuesday.

Seven Russian planes and two Chinese planes had entered the Korea Air Defence Identification Zone (KADIZ) at around 10 a.m. (0100 GMT) then left, and there was no breach of its territorial airspace, South Korea's Joint Chiefs of Staff (JCS) said.

An earlier report by the Newsis news agency had said 11 planes had entered the air defence zone.

The Russian and Chinese military aircraft had been identified and South Korean fighter jets were deployed in case of any contingencies, the JCS said.

The aircraft spent about an hour in the KADIZ off South Korea's east and south coast, the Yonhap News Agency also cited South Korea's military as saying.

Chinese and Russian military aircraft typically conduct joint exercises around the Korean Peninsula once or twice a year, Yonhap reported.