Beijing on Thursday slammed Washington's "tyrannical logic" over the latest US sanctions targeting Chinese expansionism in the South China Sea, worsening tensions between the two superpowers.

In recent years, China has aggressively pursued its territorial claims in the South China Sea, building small shoals and reefs into military bases with airstrips and port facilities.

Both the US and Chinese militaries have recently ramped up their actions in the region, raising tensions between the two.

The US on Wednesday announced sanctions on two dozen Chinese companies and associated unnamed officials for taking part in building artificial islands in disputed waters.

But foreign ministry spokesman Zhao Lijian denied at a regular press briefing Thursday that the construction work had anything to do with Chinese militarisation, and said it was within the scope of territorial sovereignty.

"The US's words grossly interfere in China's internal affairs... it is wholly tyrannical logic and power politics," Zhao said.

"China will take firm measures to uphold the legitimate rights and interests of Chinese companies and individuals."

The US Commerce Department said the companies "enabled China to construct and militarize disputed outposts in the South China Sea".

The Chinese have recently conducted military exercises in the area, while the US navy has undertaken regular "freedom of navigation operations" to assert its rejection of Chinese sovereignty by sailing near islands that Beijing claims as its own.

China's military on Tuesday accused the US of deliberately flying a U-2 spyplane into a no-fly zone to disrupt live-fire drills by the People's Liberation Army.

In July the United States formally declared Beijing's pursuit of territory and resources in the South China Sea as illegal, explicitly backing the territorial claims of Southeast Asian countries against China's.

© AFP