South Korea deployed military patrol aircraft and warships to an area under its air defense zone on Tuesday as China and Russia kicked off their joint seven-day maritime drills in the area in the East China Sea without prior notice.

Korea’s Defense Ministry also called in a defense attache from the Chinese Embassy in Seoul to request that Beijing notify Korea of future military drills beforehand to prevent any accidental clashes in the overlapping areas of their air defense zones.

It is the first time that Beijing has conducted military drills in the area since Seoul expanded its air defense zone last December in response to Beijing’s unilateral demarcation of its zone last November.

“The South Korean military has strengthened its vigilance and surveillance activities in the area under Korea’s air defense zone, where China and Russia are conducting a military exercise,” Defense Ministry spokesperson Kim Min-seok told reporters.

“On top of that, we are making efforts to ensure the safety of civilian aircraft and vessels, and prevent any accidental clashes between military aircraft, as we utilize communication hotlines set up between the navies and air forces of the two countries.”

With the participation of Russia, China began its “Maritime Cooperation-2014” exercise in the East China Sea four days after it officially set a no-fly zone in the area, located just 47 km away from Ieodo, a submerged rock controlled by South Korea, and 370 km away from disputed islands called the Senkakus in Japan and the Diaoyu in China.

Beijing has deployed eight naval ships, two submarines, nine military aircraft and six choppers, with Moscow sending six warships for the exercise. The drills proceeded amid the long-simmering territorial dispute over the Senkaku-Diaoyu Islands.

Late last year, Beijing’s abrupt expansion of its air defense zone in the conflict-laden East China Sea prompted diplomatic friction with Seoul, as the zone included Ieodo, which lies within the overlapping exclusive economic zones of South Korea and China. Seoul has operated a scientific research facility on Ieodo since 2003 to strengthen its effective control of the rock.

Beijing’s unilateral announcement of the expanded air defense zone has also unnerved regional powers as it was perceived as a significant sign of China’s expansionist ambitions and intention to challenge the status quo.

The air defense identification zone is not part of a country’s airspace. Not bound by international law, the zone is set up outside the territorial airspace to identify foreign military aircraft for purposes of national security.

Any foreign warplane that enters the zone without prior notification can face interception or warnings. But South Korea, China and Japan have ignored one another’s claims to the overlapping parts of their zones.

By Song Sang-ho (sshluck@heraldcorp.com)