A Russian official has said a military jet's intrusion into South Korean territorial airspace was not intentional, according to Seoul's presidential office. The official expressed "deep regret" to the defence ministry and blamed a technical glitch, South Korea said.

Russian Beriev A-50 (Picture source: Alex Beltyukov)

Russia said its plane was taking part in joint air patrol exercises by Russian and Chinese aircraft over the East Sea and the East China Sea, which was the first ever air patrol between the two countries.

A total of three Russian and two Chinese military aircraft entered the Korea Air Defense Identification Zone (KADIZ) on Tuesday morning, including an A-50 Russian warplane which briefly violated South Korea's airspace before leaving.

South Korea says its jets fired flares and machine-gun warning shots when the Russian plane intruded. It also deployed F-15 and F-16 planes to intercept it. Russian and Chinese bombers and reconnaissance planes have occasionally entered the zone in recent years, but this is the first incident of its kind between Russia and South Korea.

"Russia said its Defense Ministry will immediately launch a probe and take necessary steps," presidential office spokesperson Yoon Do-han said.