'Hong Kong is China's Hong Kong': Beijing hits back at U.S. for 'slandering' city's new security law

China's embassy hit back against U.S. criticism of Hong Kong's new national security law on Thursday, saying the U.S. should "respect China's sovereignty."

Hong Kong lawmakers passed a new national security law on Tuesday which critics say grants the government more power to quash dissent.

The law includes stringent penalties for a wide range of actions including "treason" and "insurrection" which are punishable by life imprisonment.

Following the announcement, the U.S. State Department described the threats outlined in the law as "poorly defined and incredibly vague."

"We believe that these kinds of actions have the potential to accelerate the closing of Hong Kong's once open society," spokesperson Vedant Patel said. 

China's embassy in the U.S. responded by saying that other countries should not interfere in its affairs. 

"Hong Kong is China's Hong Kong. Hong Kong affairs are purely China's internal affairs, which no country is in the position to point fingers at or interfere in," a spokesperson said on Wednesday.

"We urge the U.S. side to respect China's sovereignty, adhere to the principles guiding the international law and the basic norms governing international relations, and immediately stop interfering in Hong Kong affairs which are China's internal affairs."

Hong Kong's Legislative Council had introduced the bill known as Article 23 on March 8 and Chief Executive John Lee had urged to pass the law "as soon as possible" amid an "increasingly complex" geopolitics backdrop.

Earlier this month, China's Foreign Minister Wang Yi said the U.S. had been devising "new ways to suppress China," and its accusations against Beijing had reached an "unbelievable degree."

"There is some progress in the China-U.S. bilateral relationship, but we have to point out that U.S. continues to persist with a wrong understanding of China," he said.

— CNBC's Evelyn Cheng and Clement Tan contributed to this story.