China will not simply sit back and watch if months of protests in Hong Kong develop into an "uncontrollable" situation, Beijing's ambassador to Britain said Monday.
"I think the Hong Kong government is trying very hard to put the situation under control," Liu Xiaoming told a London press conference, as fresh violence erupted after months of protests.
"But if the situation becomes uncontrollable, the central government would certainly not sit on our hands and watch. We have enough resolution and power to end the unrest."
The comments from China's top diplomat in London came after a brief and rare deployment of Chinese troops in Hong Kong over the weekend to clean up streets.
The People's Liberation Army has a barracks in an upper-class district of Hong Kong.
Asked about a possible intervention, the envoy said: "They are there to show Chinese sovereignty and they are there for defence purposes."
Liu Xiaoming also warned against "external interference" in internal Chinese affairs, singling out Britain and the United States and accusing them of condoning violence by protesters.
Last week, a Hong Kong government minister was injured as pro-democracy campaigners surrounded her when she arrived for a speaking engagement in London.
Britain, the former colonial power in Hong Kong, on Monday said it was "seriously concerned" about the latest outbreak of violence.
Riot police sought to dislodge several hundred pro-democracy protesters who occupied a university and set fire to its main entrance.
Police -- who have been attacked with arrows in recent days -- used tear gas and fired live rounds.
"It is vital that those who are injured are able to receive appropriate medical treatment, and that safe passage is made available for all those who wish to leave the area," the Foreign Office said.
It called for an end to the violence, "and for all sides to engage in meaningful political dialogue ahead of the District Council elections on Sunday".
The envoy said the "illegal, violent activities" of protesters had "pushed Hong Kong into an extremely dangerous situation".
The unrest had eroded China's "one country, two systems" approach to governing Hong Kong, although he said Beijing remained committed to the policy.
He accused demonstrators of trying to destabilise and paralyse Hong Kong to "seize power" in a push for independence.
"Hong Kong citizens live under black terror created by violent extremism with their life and property under severe threat," he said.
Hong Kong's economy has slumped into technical recession because of the months of protests, denting its international image as a place to do business, he said.
"The once 'Oriental pearl' is turning into the 'Oriental scar'. Hong Kong, the 'fragrant harbour', is sliding into 'an abyss of chaos'.
"The future of Hong Kong, if such a situation continues, would be unimaginably dreadful."