A biennial naval drill took place in a part of the sea that lies within China’s newly established Air Defence Identification Zone (ADIZ)

South Korea and Japan have carried out a naval drill in the East China Sea, deploying destroyers and maritime helicopters in a region where both countries are involved in a dispute with China.

A biennial naval drill took place in a part of the sea that lies within China’s newly established Air Defence Identification Zone (ADIZ).

While officials said the drill had been planned before China’s November 23 announcement, both countries have appeared to signal that they will not follow China’s regulations by deploying helicopters without filing flight plans with China.

The drill took place near the Leodo reef, which is controlled by South Korea but lies within the exclusive economic zones of China and South Korea. The area also falls within both Chinese and South Korean air defence zones, which are not territorial claims but a defined airspace within which countries track aircraft heading towards their territory.

Both countries “did not submit flight plans to the Chinese authority based on their principle not to recognise the zone,” the Seoul-based Yonhap news agency reported.

China on Thursday reiterated that it viewed its moves as “just, reasonable and comply[ing] with international practices,” Foreign Ministry spokesperson Hong Lei told reporters.

While China has hit out at Japan’s criticism of the zone, pointing out that Tokyo had established a bigger ADIZ in 1969, it has taken a more measured reaction to South Korean concerns.

On Thursday, two South Korean airlines said they had begun complying with Beijing’s requests to file flight plans, despite its government’s official opposition to the setting up of the ADIZ. Japanese airlines initially filed flight plans, but stopped doing so subsequently in accordance with Tokyo’s official position.

China has said it would deploy “emergency” defensive measures if aircraft entered the zone without filing plans. Civilian and other aircraft that were not seen as posing a threat would merely be “identified” and “tracked”.

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