“We must warn all the ugly forces that try to challenge the central authority and undermine the bottom line of the ‘one country, two systems’ principle,” the news agency said on Sunday.

It added: “The central government will not sit idly by and let this situation continue,” while reiterating that it’s sticking to the one country, two systems regime.

The unrest is Hong Kong is growing, with fresh violence at the weekend amid four days of planned rallies.

Police used tear gas in parts of the Kowloon district on Saturday night to try to disperse crowds and re-open blocked roads.

The Hong Kong government said the protests go “way beyond the boundary of freedom of expression in a civilized society,” while noting that some protesters were suspected to have deliberately damaged the national flag.

“The flag is a symbol of the country, so the act was a public trampling on the country’s dignity and an insult to all Chinese nationals, including Hong Kong residents,” Xinhua said.

“Maintaining the dignity of the flag is to safeguard the dignity of the country, the nation and the entire Chinese people.”