The news agency’s commentary did not threaten specific action to end the protests, other than repeating unwavering support for the Hong Kong government and police actions to end them.

But the commentary – the latest in a series of strongly worded statements from Beijing – did lay out three bottom lines “that must not be crossed”.

“No one should harm [China’s] national sovereignty and security; no one should challenge the power of the central authorities and the authority of the Basic Law of the HKSAR; no one should use Hong Kong to infiltrate and undermine the mainland,” it said, referring to the city’s formal title of Special Administrative Region.

“Anyone who dares to infringe upon these bottom lines and interfere in or damage the ‘one country, two systems’ principle will face nothing but failure and will be held accountable by the country’s constitution and the HKSAR’s Basic Law.”