China said on Wednesday that it was deeply shocked and dissatisfied with the Philippine president's remarks likening China to Nazi Germany, warning Manila to stop provoking Beijing on the South China Sea issue.

Foreign Ministry spokeswoman Hua Chunying said that the Philippines has tried to occupy Chinese islands for decades and has kept "colluding with countries outside the region to stir up trouble and sling mud at China".

"I once more seriously warn certain people in the Philippines to cast aside their illusions and repent, stop provocations and instigations, and return to the correct path of using bilateral channels to talk and resolve this dispute," she said.

During a speech in Japan on Wednesday, Philippine President Benigno Aquino compared China's actions to Nazi Germany's territorial expansion before the outbreak of World War II.

Tensions have risen recently as the Philippines, as well as the United States and Japan — two nations that are not directly involved in the issue — repeatedly criticize China over its construction on some of its islands in the South China Sea.

China has said its projects mainly aim to provide a civilian service that will benefit other countries.

US President Barack Obama conceded on Monday that "it may be that some of their (China's) claims are legitimate", but he urged China to stop construction on the islands. The US has sent reconnaissance planes over Chinese islands with reporters on board.

Chinese Ambassador to the US Cui Tiankai told The Wall Street Journal it was "very surprising to us that the US has overreacted to the situation and is escalating the situation."

He said China is more concerned than anybody about the safety and freedom of navigation in the region, given China's huge trade volume going through the South China Sea.

"If somebody wants to see escalation of tension, then that could be used as an excuse for advancing their military deployment, for setting up Cold War-type alliances and for setting up new missile defense systems," he said.

During Aquino's visit, Tokyo and Manila are likely to agree to start talks on a framework for the transfer of defense equipment and technology. Japan last year eased restrictions on arms exports set after World War II.

"As a major victim of Japan during the war, it is really cynical for the Philippines to unite with Japan and link China to Nazi Germany," said Chen Qinghong, a Southeast Asian studies researcher at the China Institutes of Contemporary International Relations.

"Manila wants Tokyo to help press Beijing on the South China Sea issue. And Japan — which is under great international pressure for its attitude on history as the 70th anniversary of the end of World War II approaches in August — seeks to transfer the regional focus."