China expressed firm opposition to U.S. blatant interference in China's internal affairs, Chinese Foreign Ministry spokesperson Mao Ning said at a regular press briefing on Monday.

Mao's remarks came after the U.S. State Department Spokesperson announced new visa restrictions on officials of the Chinese Central Government and the Hong Kong Special Administrative Region (HKSAR) government in a statement released last week on the verdict issued by the Hong Kong court on some of those involved in the case of conspiring to commit subversion.

Mao said that the United States has deliberately attacked the principle of "one country, two systems," smeared the Law on Safeguarding National Security in the Hong Kong SAR, irresponsibly commented on democracy and freedoms in Hong Kong, sought to meddle with HKSAR's judicial matters and abused visa restrictions.

"Such moves blatantly interfere in China's internal affairs, violate international law and basic norms governing international relations. China strongly deplores and opposes it," said Mao.

Mao added that the so-called "primary election" organized by those involved in the case who are anti-China and sought to destabilize Hong Kong amounts to a serious challenge to the constitutional order in Hong Kong and endangers national security.

"Among the defendants involved in the case, 31 have already pleaded guilty," Mao said, noting that it is reasonable and lawful for the law enforcement and judicial authorities in the HKSAR to carry out their duties in accordance with the law, and punish all acts that undermine national security, and that it is firmly supported by the Central Government.

Mao stressed that Hong Kong affairs are purely China's domestic affair that brooks no external interference.

China urges the United States to earnestly respect China's sovereignty and the rule of law in Hong Kong, and abide by international law and basic norms governing international relations, the spokesperson said.

"The United States should not in any way meddle with Hong Kong affairs," Mao said, adding that if the United States implements the visa restrictions on officials of the Central Government and the HKSAR government, China will take firm countermeasures.