BEIJING (REUTERS) - China has placed US companies Lockheed Martin Corp and Raytheon Technologies Corp under sanctions over US arms sales to Taiwan, at least the third time it has announced punishments against the US companies.

The sanctions are countermeasures against the two companies over a US$100 million (S$135 million) Feb 7 arms sale that "undermined China's security interests, seriously undermined China-US relations and peace and stability in the Taiwan Strait", foreign ministry spokesman Wang Wenbin said at a regular news briefing.

Beijing says that the self-ruled island of Taiwan is a breakaway province that must be reunified with the mainland.

"In accordance with the relevant stipulations in China's anti-foreign sanctions law, the Chinese government has decided to take countermeasures on the infringing acts of Raytheon Technologies and Lockheed Martin," Mr Wang said.

"Both are military enterprises that have long participated in US arm sales to China's Taiwan region."

No further details were given on the nature of the sanctions.

This is the first time the companies have faced sanctions under China's new anti-foreign sanctions law drawn up last year in response to US sanctions against Chinese companies.

On at least two previous occasions China has announced sanctions against Lockheed and Raytheon, in 2019 and 2020, though Beijing provided no further details.

The United States does not sell weapons to China.

However, the United States is bound by the 1979 Taiwan Relations Act to provide Taiwan with the means to defend itself, and US weapons sales always attract China’s anger.

China has over the past two years stepped up its military and diplomatic pressure against Taiwan, whose government says it wants peace but will defend the island if attacked.

China regularly says Taiwan is the most important and sensitive issue in its ties with Washington, which are also strained over trade and human rights disputes.