The United States called Tuesday for calm between Japan and China after Beijing sent ships to disputed islands in the East China Sea in response to Tokyo's purchase of them.

"We think, in the current environment, we want cooler heads to prevail, frankly," said Kurt Campbell, the assistant secretary of state for East Asian and Pacific affairs.

Campbell, echoing remarks this weekend by Secretary of State Hillary Clinton at the end of a tour of Asia, said that calm was critical because the region serves as a "cockpit of the global economy."

"The stakes could not be bigger," Campbell said at the Center for Strategic and International Studies, a think tank.

"We believe that peaceful dialogue and the maintenance of peace and security is of utmost importance always but particularly now in this set of circumstances," Campbell said.

In line with repeated US statements, Campbell said that Washington did not take positions on the various and increasingly bitter territorial disputes around Asia.

China said that it was dispatching two marine surveillance ships to "assert its sovereignty" over the islands in the East China Sea known in Chinese as the Diaoyu and in Japan as the Senkaku islands.

The move came after Japan said it would nationalize the islands through a purchase from private Japanese landowners. The islands lie near potentially lucrative mineral resources and are strategically close to the Taiwan Strait.

Asia has been riveted by a series of disputes including tensions in the South China Sea and a flareup between US allies Japan and South Korea over islets in the Sea of Japan, which Koreans call the East Sea.

Clinton, speaking Sunday at an Asia-Pacific summit in Vladivostok, Russia, said that she urged Japan and South Korea to "lower the temperature and work together."

More broadly in Asia, Clinton warned that it was "not in the interest of the United States or the rest of the world to raise doubts and uncertainties about the stability and peace in the region."

China sends ships to islands purchased by Japan
Beijing (AFP) Sept 11, 2012 - China has dispatched two patrol ships to "assert its sovereignty" over islands at the centre of a row with Japan, state media said Tuesday, as Tokyo completed its purchase of the disputed territory.

The two marine surveillance ships had reached the waters around the Diaoyu islands -- known in Japan as the Senkaku islands -- and would "take actions pending the development of the situation," the Xinhua news agency said.

The arrival came as the Japanese government announced it had completed its planned purchase of the islands, which lie in a strategically important shipping area with valuable mineral resources thought to be nearby.

"This should cause no problem for Japan's ties with other countries and regions," said Japan's Chief Cabinet Secretary Osamu Fujimura.

"We have absolutely no desire for any repercussions as far as Japan-China relations are concerned. It is important that we avoid misunderstanding and unforeseen problems," he told reporters.

Beijing had earlier summoned the Japanese ambassador and lodged a strong protest over Tokyo's move to purchase the islands, while vowing to take counter-measures.

Chinese Premier Wen Jiabao said the islands were "an inherent part of China's territory" and vowed his country would "never ever yield an inch" on its sovereignty.

However, the ships China dispatched were from the State Oceanic Authority and not military vessels and analysts downplayed the significance of the move, saying the deal may even allow Beijing and Tokyo to temper tensions.

"That some patrol vessels were deployed in the vicinity of the islands was almost inevitable, but now, at least, there is no longer a risk that some nationalist Japanese politician would gain control of the islands," said China expert Jonathan Holslag.

"Most decision-makers in Beijing are relieved that the Japanese national government bought the Senkaku/Diaoyu Islands," added Holslag, head of research at the Brussels Institute of Contemporary China Studies.

On Sunday, Chinese President Hu Jintao urged Japanese Prime Minister Yoshihiko Noda not to go ahead with the purchase in brief talks held on the sidelines of the Asia-Pacific economic summit in Vladivostok.

"China-Japan relations have recently faced a severe situation due to the Diaoyu Island issue," a foreign ministry statement quoted Hu as telling Noda.

"Japan must fully recognise the gravity of the situation and should not make wrong decisions."

Officials at China's State Oceanic Administration, which dispatched the two surveillance ships, were not immediately available to clarify to AFP whether the vessels were armed.

Often testy Japan-China ties took a turn for the worse in August when pro-Beijing activists landed on one of the islands.

They were arrested by Japanese authorities and deported. Days later about a dozen Japanese nationalists raised their country's flag on the same island, Uotsurijima, prompting protests in cities across China.

Japan's government currently leases four islands and owns a fifth. It does not allow people to visit and has a policy of not building anything there.

State television and all major Chinese dailies in China Tuesday highlighted Beijing's condemnation of the purchase. Around 200 people in eastern Shandong province took to the streets Tuesday to protest, carrying banners and singing China's national anthem.

The islands, which lie around 200 kilometres (125 miles) from Taiwan and 2,000 kilometres from Tokyo, are also claimed by Taipei, which strongly protested the Japanese move on Tuesday.

"We strongly demand that the Japanese government revokes this move," Taiwan's foreign minister Timothy Yang told reporters in Taipei.

"Japan's unilateral and illegal action cannot change the fact that the Republic of China (Taiwan's official name) owns the Diaoyu islands."