Beijing has hit out at Manila for repairing a crumbling ship serving as its outpost in the disputed South China Sea, branding the Philippines as a "hypocritical troublemaker and rule breaker".

The Philippine military deliberately grounded the 100-metre (328-foot) World War II-vintage BRP Sierra Madre atop the Second Thomas Shoal in 1999 in an effort to check the advance of China, which four years earlier occupied Philippine-claimed Mischief Reef some 40 kilometres (25 miles) away.

Philippine Navy spokesman Colonel Edgard Arevalo said Wednesday that the rust-ridden vessel was being repaired to ensure the ship remains livable for a tiny unit of marines guarding the reefs.

The move drew a vehement protest from China, with foreign ministry spokeswoman Hua Chunying accusing Manila of attempting to "permanently steal" the outcrops, while insisting that the reefs and other islets in the Spratlys were Chinese territory.

"China strongly protests and firmly opposes such an act," Hua said in a statement on Wednesday.

She also argued that Manila had gone back on its word by repeatedly promising to remove the ship -- a claim the Philippines denies.

"The relevant activity fully exposed the Philippines' hypocrisy and that it is a double dealer," said Hua.

"It once again proved that the Philippines is truly a troublemaker and rule breaker in the region."

The comments come as Beijing pursues a rapid programme of artificial island construction in the South China Sea, facilities which it has said will serve military as well as civilian purposes.

At the same time, the Philippines has asked a United Nations-backed tribunal to declare China's claim over most of the resource-rich South China Sea illegal.

The arbitration body based in The Hague is expected to decide within months whether it has jurisdiction over the case.

The Philippines regularly rotates a group of around nine marines aboard the Sierra Madre, a tank-landing ship which first saw service for the United States navy in World War II. It was acquired by the Philippine Navy in the 1970s.

Hua said China was "determined to protect its territorial sovereignty and maritime rights and interests".

"We again urge the Philippines to immediately stop its illegal infringement activities and live up to its promise by removing the vessel," she said, adding that Beijing "reserves the right to take further steps".

Vietnam, Taiwan, Malaysia and Brunei also have overlapping claims in the area, which straddles major shipping lanes.