BEIJING (Reuters) - China is concerned over news that social network Twitter has locked the account of its embassy in the United States, the foreign ministry said on Thursday. Chinese authorities were confused by the move, foreign minisry spokeswoman Hua Chunying told a regular briefing. On Thursday, Twitter said it locked the account over a message that defended China’s policies in its far western region of Xinjiang, saying it had violated the U.S. firm’s policy against “dehumanization”.