China criticized the United States and Britain on Tuesday for failing to "severely condemn" protesters who set fire to a civilian in Hong Kong, warning the two countries to stop interfering in China's internal affairs.

"If the United States and the United Kingdom really oppose violence and call for restraint as they claim, why don't they severely condemn such attacks on ordinary civilians?" Foreign Ministry spokesman Geng Shuang said at a regular press briefing.

Not doing so, "once again exposed their double standards and ulterior motives," Geng added.

In separate statements, the United States and Britain both called for dialogue and restraint on all sides after Monday saw some of the worst violence in Hong Kong since mass protests began in the semi-autonomous Chinese territory in June.

"We condemn violence on all sides, extend our sympathies to victims of violence regardless of their political inclinations, and call for all parties, police and protesters, to exercise restraint," U.S. State Department spokeswoman Morgan Ortagus said in a statement.

Meanwhile, British Prime Minister Boris Johnson's office, in a statement, urged "calm and restraint on all sides," adding that "political dialogue is the only way forward," according to AFP.

A man was hospitalized with burns after being doused with a flammable liquid and set on fire by protesters, while a police officer shot a 21-year-old protester. Both remain in critical condition, hospital authorities said.

A video circulating on social media shows the civilian apparently arguing with protesters before being set ablaze.

Other footage uploaded to media sites showed a police officer shooting a mask-wearing protester -- while grappling with another masked man -- at point-blank range on Hong Kong Island.

"We can see clearly through the video that the mob attacked the police first, and the police handled it completely according to law. So it is clear who is right and wrong," Geng said, adding that seizing firearms from police and attacking a policeman who is enforcing the law is not allowed anywhere in the world.

While reiterating "Hong Kong affairs are purely the internal affairs of China," Geng urged the United States and Britain to "earnestly respect China's sovereignty and be careful in their words and deeds on Hong Kong-related issues."

Related coverage:

Japanese man injured in Hong Kong as protests escalate

Hong Kong protesters disrupt traffic for 2nd day, clash with police