China's deployment of surface- to-air missiles on an island in the South China Sea sharply raises the level of militarisation in the region, analysts say, with several regional governments voicing their concern yesterday.
The Paracel chain is also claimed by Vietnam and Taiwan.
Taiwan President-elect Tsai Ing- wen said the deployment raised regional tensions. "We urge all parties to work on the situation based on principles of peaceful solution and self-control," she told reporters.
Separately in Hanoi yesterday, several dozen Vietnamese waved banners and shouted anti-Chinese slogans to mark the 37th anniversary of China's invasion of their country in 1979, when the neighbours fought a brief but bloody border war. There was no official reaction to the missile deployment from Vietnam's government, even until yesterday evening.
There is little that Hanoi can do, said Singapore-based Dr Ian Storey, an Iseas-Yusof Ishak Institute senior fellow. "Vietnam will condemn the deployment but it can't force China to remove the missiles," he said.
Japan's Chief Cabinet Secretary Yoshihide Suga said in Tokyo that there were "serious concerns" over China's "unilateral move to change the status quo" in the region, and "we cannot accept this fact".
Japan and China have routinely clashed over ownership of the Tokyo-controlled Senkaku Islands in the East China Sea. Japan administers the uninhabited islands under that name, but China also claims them and calls them the Diaoyu Islands.
Beijing also claims almost the entire South China Sea, a claim which overlaps with that of several Asean members but most critically Vietnam and the Philippines.
In Manila, President Benigno Aquino's spokesman, Mr Edwin Lacierda, told reporters that the deployment of the missiles to Woody Island "exacerbates" tensions.
"Again, we'd like to emphasise that it will not be to the interest of any nation, considering that a large percentage of trade happens in those seas, to exacerbate the situation or to get us to a point where tensions may arise," he said.
Mr Nguyen Ngoc Truong, president of the Centre for Strategic Studies and International Development in Hanoi, said: "The missile (deployment) is a step in preparation to militarise the South China Sea."
He noted that the news of the missile deployment came at the same time as the United States-Asean summit in California. "It's a provocative action against the countries holding the summit in Sunnylands. It's not good timing, it's provocative."
In an e-mail, Emeritus Professor Carl Thayer of the Australian Defence Force Academy wrote that "China's actions raise the stakes and risks for future US maritime reconnaissance patrols in waters surrounding the Paracels".
He wrote that Woody Island had been militarised already for quite some time, with a recently extended 3,048m airstrip, hangars and jet fighters deployed.
But the deployment of a sophisticated and lethal air defence system, he said, "is no doubt in response to US aerial activities and the recent freedom of navigation operational patrol near Triton Island" of the Paracels.
A US missile destroyer last month sailed close to Triton, eliciting a rebuke from Beijing, which said the action had "severely violated the law".