Joint Chinese and Russian naval exercises lasting until next Monday involve portions of Korea's new air defense identification zone that was announced in December last year.
The area of the joint naval drill covers parts of the East China Sea where the air defense identification zones of Korea, China and Japan overlap. This is the first time China has staged naval drills in this area.
Foreign aircraft must notify the Joint Chiefs of Staff 24 hours in advance if they want to enter the zone, and report their location once they do.
The joint naval drill is aimed at improving China's and Russia's capacity to deal with maritime security threats and counter the defense alliance formed by Korea, the U.S. and Japan.
Korea stepped up surveillance and reconnaissance in its southwestern air defense zone Tuesday and summoned a military attache from the Chinese Embassy in Seoul to express concern.