The navies of Japan and South Korea yesterday said they had carried out a joint maritime rescue drill in international waters covered by China's new air defence identification zone.
Japan's Maritime Self Defense force used two warships and a helicopter, while its South Korean counterpart also used several pieces of military equipment for the routine training, a Japanese navy spokesman said.
The Japanese military did not inform China about the use of the helicopter, he added.
"It was conducted within what China said was its ADIZ (air defence identification zone)," he said. "The drill had been planned for a long time, since before China's announcement. It was not organised in reaction," he added.
Last month, China declared the new ADIZ over a tranche of the East China Sea, including islands disputed with Japan as well as South Korea's ADIZ.