Russian military planes have entered the KADIZ more than 13 times so far this year, according to government data.

On July 23, a Russian A-50 early-warning aircraft intruded into South Korea's territorial airspace over the country's easternmost islets of Dokdo in the East Sea twice, leading the Air Force to fire hundreds of warning shots.

The intrusion came shortly after two other Russian aircraft and two Chinese military aircraft breached the KADIZ between Dokdo and the eastern island of Ulleung several times in unusual joint air maneuvers between the two countries.

In August, two Russian TU-142 patrol planes also violated the KADIZ over the East Sea.

In order to prevent such cases, South Korea and Russia have been pushing to set up a military hotline between their air forces to exchange their flight information, according to Seoul's Joint Chiefs of Staff.

The two sides began discussing the matter in 2004 and wrapped up consultations on the draft of the envisioned MOU in November last year, it added.

The air defense zone was first drawn in 1951 by the US Air Force during the 1950-53 Korean War to prevent air clashes between nations surrounding the Korean Peninsula. Last year, Seoul expanded it to counter China's unilateral decision to expand its own to cover a reef and other islands off the southern coast.

The air zone is not part of a country's air space and not bound by international law. (Yonhap)