Hina's recent conduct in its bitter dispute with Japan over the ownership of islands, fisheries and seabed resources in the East China Sea raises some geopolitical storm warnings for South-east Asia.

While often seen as separate issues, the conflicting sovereignty claims of China and Japan over the Senkaku islands in the East China Sea are closely connected with Beijing's much larger territorial and maritime boundary claims in the South China Sea.

The Chinese claims in South-east Asia's maritime heart overlap with those of atoll and reef ownership by Vietnam, the Philippines, Malaysia and Brunei, and with exclusive economic zone and continental shelf resource claims by those four countries and Indonesia.

In this context, South-east Asian strategic analysts will have watched with considerable alarm the virulent outbreak of Chinese nationalism and anti-Japan protests following the Japanese government's move earlier this month to buy three of the Senkaku islands from their private owners.

The government's aim was to pre-empt a similar plan by Japanese right-wingers with a strong anti-China agenda. All the islands in the Senkaku group are administered by Japan but have been kept uninhabited and undeveloped to try to take the heat out of the sovereignty dispute with China.

Anti-Japanese protests swept dozens of Chinese cities. Outbreaks of vandalism, arson and looting damaged Japanese factories, stores and restaurants, causing many to close temporarily.

For several days last week, until the Chinese authorities decided to halt the protests, it seemed they might spiral out of control, raising the risk of an armed confrontation between Japan and China as the latter sent paramilitary ships and fishing boats into and around Japanese territorial waters in the Senkaku islands.

Meanwhile, two other things were causing unease in South-east Asia. China was threatening economic reprisals against Japan over their maritime dispute and its state-owned media was reporting small but significant anti-Japan protests by "overseas Chinese".

These protests were not just in Europe, Africa, South America and Australia but also in South-east Asia where over 20 million people of Chinese descent have settled and, in many cases, become citizens of their adopted countries.

China has become Japan's largest trading partner in recent years, just as China has become the top trading partner of most South-east Asian economies. Beijing uses this position as leverage in territorial disputes.

On Sept 13, three days after Japan's nationalisation of the Senkaku islands, China's Vice-Minister of Commerce Jiang Zengwei openly encouraged Chinese consumers to boycott Japanese goods.

Mr Jin Baisong, deputy director of the Chinese trade studies department in an agency affiliated with the Ministry of Commerce, went further.

Writing in the China Daily last Monday, he called for selective economic sanctions against Japan, arguing that an analysis of two-way trade and investment suggested that Japan was more reliant on China for economic health than vice versa, and that China was much better able than Japan to afford a loss of exports.

China, Mr Jin wrote, "has the capability to impose sanctions on other countries now that it is the (world's) second-largest economy, has the largest foreign (exchange) reserves, and is the largest exporter and second-largest importer".

In the dispute with the Philippines earlier this year over ownership of the Scarborough Shoal in the South China Sea, Beijing deployed paramilitary ships and fishing boat flotillas, and used economic reprisals and connections with the Chinese in the Philippines in its attempts to take control of the shoal.

The repetition of these tactics in the Senkaku dispute shows that they have become part of China's policy to enforce its sovereignty and jurisdiction claims in contested maritime areas. The implications are potentially more serious for South-east Asia than for Japan, partly because there are far more Chinese living in the region whose loyalty and identity could be tested than there are in Japan.

In the East China Sea, the disputed island and maritime zone between China and Japan amounts to around 68,000 sq km. However, Beijing claims sovereignty and other forms of jurisdiction over about 80 per cent of the semi-enclosed South China Sea, an area that amounts to about three million sq km.

The potential commercial and strategic value of the South China Sea is far greater for Beijing than that of its relatively small claim against Japan in the East China Sea.

As China's economic and military strength grows, it can be expected to assert its claims in the maritime centre of South-east Asia more insistently.

If China's claims in the South China Sea were recognised or enforced, Malaysia, Brunei and Indonesia would all find themselves sharing maritime boundaries with China, as Vietnam already does and the Philippines does via Taiwan. In the Philippines' case, its maritime border with China would suddenly become far longer, stretching the whole length of its western coastline overlooking the South China Sea. Vietnam also has a land border with China, as do Myanmar and Laos.

So the world's most populous nation would become the immediate maritime neighbour of three additional South-east Asian countries, including the region's biggest economy, Indonesia. Seven out of the 10 Asean member states would be adjacent to China, which would also become a close geographical neighbour of Singapore.

With proximity would come greater Chinese influence, as well as leverage in disputes.

It would be a different operating environment for South-east Asia - one that is more China-centric and with less room to manoeuvre and seek a countervailing presence from outside powers.

The writer is a visiting senior research fellow at the Institute of Southeast Asian Studies.