Speaking at a press conference in London on Thursday, Liu said that the central government would have to act if the situation became “uncontrollable” and “would not sit on its hands and watch”.

“We have enough solutions and enough power within the limit of the Basic Law to quell any unrest swiftly,” Liu said.

His comments came just hours after a group of legal analysts told a press conference in Beijing organised by the State Council that the city’s Basic Law has provisions that would allow for the deployment of Chinese military forces within Hong Kong.

“We hope this will end in an orderly way. In the meantime we are fully prepared for the worst,” Liu said, adding that “extremists masquerading as democracy protesters are dragging Hong Kong down a dangerous road”.

Meanwhile, Wu made similar remarks on Wednesday in an interview with ZDF television, but he did not directly refer to Merkel’s comments.

“The current situation first and foremost is the responsibility of the [Hong Kong] SAR government,” Wu said. “But if the SAR government fails to control the situation, the central government would, of course, provide assistance.”

Commenting on reports that members of the People’s Armed Police, a Chinese paramilitary force, have been seen parading in Shenzhen just across Hong Kong, Wu said it was a “normal deployment of the Chinese armed forces within the territory”.

Meanwhile, John Bolton, the US National Security Adviser, warned in an interview with Voice of America that any “missteps” on Hong Kong would trigger a strong response from the US Congress.

“If Hong Kong loses that reputation [for rule of law] because of a bad decision by the Chinese government, they’ll have significant economic consequences in China this time,” Bolton said.

“And I can tell you from what I’ve heard, just in the past few weeks, the mood in Congress is very volatile at this point, and a misstep by the Chinese government, I think, would cause an explosion on Capitol Hill.”