China on Thursday criticized new US sanctions on Chinese firms involved in Beijing's expansionism in the South China Sea, saying the measures were "illegal" and driven by "tyrannical logic."

China has sought to bolster its vast territorial claims in the contested waterway, one of the world's busiest trade routes, by building artificial islands and equipping them with military bases, ports and runways. The latest US sanctions, announced on Wednesday, target Chinese officials and 24 companies for their role in the construction of these facilities.

"The relevant US acts grossly interfere in China's internal affairs, violate international law and relevant international norms, which are totally out of tyrannical logic and power politics,'' Zhao Lijian, a spokesman for the Chinese Foreign Ministry, said.

Read more:South China Sea — what you need to know

Washington rejects Beijing's claims in the South China Sea, parts of which are also claimed by other countries, including the Philippines, Vietnam, Malaysia and Taiwan.

The US Commerce Department said the 24 penalized companies had infringed on other nations' claims by enabling China to "militarize disputed outposts," and had therefore been added to a blacklist limiting their access to US products. 

Zhao said the construction work on islands had nothing to do with Chinese militarization and was "within the scope of sovereignty."

China would "take firm measures to resolutely safeguard the legitimate rights and interests of its enterprises and individuals," he added, without providing specific details. 

'Not going to cede ... an inch'

Tensions between Washington and Beijing have soared in recent weeks, with both countries accusing each other of deliberate provocation in the South China Sea.

The superpowers have also locked horns over a string of other issues, including technology, international trade, human rights abuses, Hong Kong's autonomy, and Beijing's handling of the coronavirus outbreak.

US Defense Secretary Mark Esper said Thursday that the Chinese People's Liberation Army was pursuing "an aggressive modernization plan," and that the Indo-Pacific was the epicenter of a "great power competition with China."

Speaking in Hawaii, he added that the US was "not going to cede this region, an inch of ground if you will, to another country, any other country that thinks their form of government, their views of human rights … [are] better than what many of us share."

Read more: What is China's world order for the 21st century?

China, which is currently holding live-fire military drills in the South and East China Seas, accused the US on Wednesday of deliberately flying a spy plane into a no-fly zone to disrupt the exercises.

The US frequently sends military ships and planes near disputed areas on "freedom of navigation" operations to challenge Beijing's territorial claims.

According to reports by the Hong Kong-based South China Morning Post, China on Thursday fired two medium-range missiles into the South China Sea in an apparent warning to Washington. The Chinese Ministry of Defense said the People's Liberation Army was conducting military exercises in the area, but gave no confirmation that missiles had been fired.

A Defense Ministry spokesman said China was not scared of "provocation and pressure" from the US, and accused "certain US politicians" of trying to fan tensions ahead of the presidential elections in November.

"This kind of behavior puts the lives of frontline officers and soldiers on both sides at risk," ministry spokesman Wu Qian told reporters.

Read more: Is China taking advantage of COVID-19 to pursue South China Sea ambitions?

Taiwan warns of 'potential for accidents'

The sharp deterioration in US-China relations prompted Taiwan on Thursday to sound the alarm about the risk of conflict accidentally breaking out.

"There continue to be significant concerns over the potential for accidents, given increased military activity in the region," President Tsai Ing-wen told a forum organized by the Australian Strategic Policy Institute on Thursday.

"Therefore we believe it would be important for all parties to maintain open lines and communication to prevent misinterpretations or miscalculations," she said. "The risk of conflict requires careful management by all the parties concerned."

nm/msh (AP, AFP, Reuters, dpa)