China said Sunday it had rejected a proposal by the Philippines for international mediation to resolve their maritime dispute in the South China Sea.

China "formally protested after a request for international mediation submitted by the Philippines over the sovereignty of the Scarborough Shoal," said a statement published on the foreign affairs ministry's website.

The head of the department of boundary and ocean affairs Deng Zhonghua informed the Philippine embassy in China of the formal protest on Saturday, the ministry said.

Deng said that given the "Scarborough Shoal is an integrative part of Chinese territory", the submission "contravenes the fundamental principles of international relations, and also inflicts serious damage on the current international order."

"China demands that the Philippines respects the sovereignty of Chinese territory and does nothing more to aggravate or complicate the situation further," the statement said.

China claims all of the South China Sea as part of its territory, even waters close to the coasts of the Philippines and other Southeast Asian countries.

The Scarborough Shoal is only about 230 kilometres (140 miles) from the Philippines' main island of Luzon, while the nearest Chinese landmass is Hainan province 1,200 kilometres to the northwest, according to naval maps.

The latest tensions began when Chinese maritime vessels blocked the Philippine navy from arresting the crews of eight fishing vessels which had entered the area.

Both sides accused each other of violating maritime laws, and on Saturday the Philippines alleged that a Chinese vessel veered dangerously close to its vessels in the area.

Amid the stalemate, the Philippines said it would seek more military assistance from its ally, the United States, to help it build a "credible defence posture" in securing its sovereignty.

China had earlier warned the Philippines against "internationalising" the issue, and its state media had quoted defence and military officials as saying they were prepared to fight for their territory.