Beijing has warned of "strong and resolute" countermeasures against fresh sanctions imposed on six mainland and Hong Kong officials by the United States.

In a strongly worded statement on Tuesday, the Commissioner's Office of the Foreign Ministry in Hong Kong accused Washington of smearing the "One Country, Two Systems" principle and slandering the city's rule of law, democracy, freedom and human rights situation.

"This is a gross interference in China's internal affairs and Hong Kong affairs, and a serious violation of the principles of international law and the basic norms governing international relations," a statement by the office said.

It also said the move to impose sanctions has once again exposed Washington's "evil intentions" of undermining the SAR's prosperity and stability, as well as containing China's development.

"China will surely take strong and resolute countermeasures," it said.

Among the officials sanctioned are Dong Jingwei, the director of the Office for Safeguarding National Security in Hong Kong; justice chief Paul Lam; and outgoing police commissioner Raymond Siu.

"The SAR police have taken lawful actions against overseas anti-China rioters, and the SAR judicial authorities have independently and impartially tried national security cases following legal procedures," the office said.

"These acts are consistent with international law and customary practice, and are just and necessary moves to safeguard national security and Hong Kong's prosperity and stability."

The Chinese embassy in the US also condemned the sanctions.

"The Chinese central government resolutely supports the law enforcement and judicial authorities of the Hong Kong SAR in carrying out their duties in accordance with the law and punishing acts that undermine national security," the embassy said in a statement.

"We urge the US side to respect the facts, stop meddling in Hong Kong affairs and interfering in China's internal affairs, and stop smearing Hong Kong's democracy and rule of law."