Japanese soldiers practised surface-to-ship missile drills Monday on an island at the gateway to the Pacific, as part of a huge military exercise that has unsettled China.

The practice in Okinawa was part of 18-day war games which Japan began earlier this month. They aim to strengthen its ability to protect remote territory, as a row with China over the sovereignty of some islands continues to rattle nerves.

No missile was actually fired during Monday's drill, which was watched by members of the media -- including a large Chinese contingent, correspondents said -- and saw men in camouflage readying SSM1 missile batteries at Camp Naha on the main Okinawan island.

"Today's drill was aimed at training cooperation among our units," the commander of the fourth anti-warship missile regiment told reporters.

Around 34,000 military personnel, six vessels and 360 aircraft are involved in the war games, which will also see the deployment of F-15 fighter jets and Patriot surface-to-air missile systems.

The exercise comes amid growing nervousness in Japan and other parts of Asia over China's surging military might, which has seen it expand its naval reach into the Pacific Ocean.

As well as its diplomatic fisticuffs with Tokyo, Beijing is also butting heads with a number of southeast Asian countries over its claims to virtually the whole of the South China Sea and the islands within it.

Okinawa is a significant location for the anti-ship missiles because it sits on one side of the main navigable strait for Chinese vessels wanting to get into the Pacific Ocean.

Tokyo has said the drill is not aimed at any specific nation, but Japanese leaders have openly expressed disquiet as China escalates its territorial claims.