China took action against nine U.S. military-affiliated companies on Wednesday in response to U.S. arms sales to Taiwan, freezing their assets within China.
This move is the latest effort to increase pressure on the United States to cease its weapons sales to the island.
Organisations and individuals within China are prohibited from engaging in transactions with the firms.
Info via Reuters, there is a little more info at the link.
Mainland China's Communist Party rulers assert the right to rule Taiwan. The people of Taiwan currently enjoy democracy and self-determination. Hence the conflict.