The PLA navy staged live-fire war games in an apparent message to the United States not to step into territorial disputes China has with its neighbours in both the South and East China seas, military experts say. China News Service said the navy sent more than 1,800 military personnel to the drill on Tuesday along the coast of Hainan, the island province that sits in the northwest corner of the South China Sea across the Gulf of Tonkin from Vietnam. Beijing says the entire sea and its island groups are China's sovereign territory, but Vietnam and several other nations also claim territory in the area. The People's Daily said the People's Liberation Army drill focused on simulating beach assaults by landing craft, amphibious tanks and fast-attack craft. It said more than 100 aircraft, tanks, mine sweepers and submarine chasers were operating offshore and were backed up by attack helicopters. State media said the exercises, dubbed Jiaolong 2010 after a mythical dragon, are held annually by the South China Sea Fleet, but that organisers had this time decided to invite, as observers, about 200 students from more than 40 countries studying at China's National Defence University and the naval and air force command schools. People's Daily photos showed that almost all the foreign students were naval and air force officials from third-world countries in Southeast Asia and Africa. Military analyst Antony Wong Dong, president of the Macau-based International Military Association, said it was rare for the exercise to be held at this time of year. He said the drill was aimed at showing China's neighbours, such as Vietnam, its ability to defend the territories it claims. 'With the wind up and the current swift in the seas in late autumn, the PLA navy seldom holds war games in the South and East China seas during this season,' he said. 'I think the drills wanted to send a stronger signal to its neighbours, like Vietnam, that the PLA is able to fight with its rivals under all weather conditions.' Ni Lexiong , a Shanghai-based military expert, said the drill was also related to the US suggestion to broker three-way talks with Japan and China over the Diaoyu Islands in the East China Sea. 'The PLA naval exercise is very similar to Japan's landing drills near the Diaoyu Islands, so I think, besides threatening Vietnam and other neighbours, we also wanted to warn the US that China is able and determined to defend and even take back the islands we lost in the South and East China seas,' he said.