China's defence ministry said on Saturday that a US report on its military which accused Beijing of ramping up land reclamation in the disputed South China Sea distorted facts, the official Xinhua news agency reported.

"The US defence department's report on China's military and security development situation distorts facts and continues to play up the 'China military threat' clich�," Chinese defence ministry spokesman Geng Yansheng was quoted as saying.

He added the US report made "groundless accusations" about China's intentions regarding national defence, space development, the Internet and military transparency.

The report repeated accusations that Beijing was staging cyber attacks to gather information on American defence programmes.

Geng made no direct mention of land reclamation in the South China Sea, but said China was justified in upholding its sovereignty in the area.

The Pentagon's annual report to Congress on the state of China's military said China had reclaimed 500 acres in the disputed waters by end-2014.

But since then, China has conducted reclamation covering 1,500 acres, US officials said Friday as the report was released.

The South China Sea is home to strategically vital shipping lanes and is believed to be rich in oil and gas.

Beijing asserts sovereignty over almost the whole of the South China Sea, including areas close to the coasts of other littoral states, using a nine-segment line based on one that first appeared on Chinese maps in the 1940s.

Washington is concerned China's efforts carry a military dimension that could undermine America's naval and economic power in the Pacific.

"The military build-up aims to maintain sovereignty, security and territorial integrity, and guarantee China's peaceful development," Geng said.