Phnom Penh: Chinese Premier Wen Jiabao has made a strong defence of his country's claim to almost all of the South China Sea after a summit of world leaders ended in bitter disagreement over how to ease tensions in the strategic and resource-rich waterways.

"China's act of defending its sovereignty is necessary and legitimate ... and we have properly handled the incidents that were not of the making of China," Mr Wen told 17 other leaders on the final day of the East Asia Summit in Phnom Penh, according to Chinese vice foreign minister Fu Ying.

US president Barack Obama told the leaders to rein in tensions over the disputed territory, but stopped short of firmly backing smaller Asian nations in their disputes with China.

"President Obama's message is there needs to be a reduction of the tensions," top US security official Ben Rhodes told journalists.

"There is no reason to risk any potential escalation, particularly when you have two of the world's largest economies — China and Japan — associated with some of those disputes," Mr Rhodes said.