Air Defence Identification Zone
The Air Defense Identification Zone is airspace over land or water in which the ready identification, location, and control of civil aircraft over land or water is required in the interest of national security. China's Defence Ministry announced its ADIZ over a vast area in the East China Sea on November 23, 2013, which covers the area around the Diaoyu islands, controlled by Japan and known as the Senkaku Islands. The establishment of this zone drew strong opposition from Japan, the US and South Korea, becoming a flashpoint in East Asian politics and security.
Japan and South Korea hold joint exercise in China’s air defence zone
Rescue exercise near Suyan Rock is seen as sending out a strong signal to Beijing, but two nations are at odds over commercial flights
Kristine Kwok and Agencies
Japan and South Korea have conducted a joint naval exercise in an area covered by China's air defence identification zone - a move that is seen as sending a firm message to Beijing.
Both countries said that while they didn't inform the Chinese authorities, the joint maritime rescue drill was planned long before Beijing announced the controversial zone over the East China Sea. Under Chinese rules, all aircraft are required to report flight plans in advance.
But yesterday's exercise added another complication to the issue, with the two countries divided over compliance by commercial flights.
Korean Air and Asiana Airlines said they would start to notify the Chinese authorities from yesterday, while Japan has told its commercial operators not to comply.
However, analysts said the Asian neighbours were sending a strong signal to China by choosing to carry out the exercise near Suyan Rock. The tiny, submerged rock has become the focus of renewed disputes between Beijing and Seoul since the air zone was declared on November 23.
A South Korean military official was quoted by the Yonhap news agency as saying that two destroyers and two helicopters from each side took part.
But neither side submitted flight plans to the Chinese authorities, the report said.
A Japanese naval spokesman confirmed the drill was conducted within China's air zone.
But he added: "The drill had been planned for a long time, since before China's announcement [of the air defence identification zone]. It was not organised in reaction [to the zone]."
South Korea extended its own air defence identification zone at the weekend to cover Suyan Rock - which it calls Ieodo - in an apparent protest against China's inclusion of the rock in its zone.
While UN maritime law says a state cannot claim territorial sovereignty over a submerged rock - Suyan lies 4.5 metres below the surface - both sides have sought administrative control over it.
Seoul currently has administrative control over the rock. It also falls under Japan's air defence identification zone, though Tokyo doesn't make claims to it.
Scott Harold, a political scientist with the Rand Corporation think tank, said Seoul intended to send a message to Beijing, through the joint exercise, that it would continue to be active around the disputed area.
He said that while relations between Japan and South Korea had been strained over the past 15 months and disputes between the two persisted, China's air defence zone had inadvertently brought the two countries closer.
"This drill is a very low-cost and politically safe way for Japan to signal to South Korea that, while they have disputes on other issues, on this one they could work together," Harold said.
Beijing has so far not responded to the joint exercise.
Bloomberg, Agence France-Presse