The Chinese government will "not sit back" against the protests in Hong Kong, said the UK's ambassador to Beijing, adding that he had "solutions".
It then became apparent that new footage was showing the establishment of armed forces in Shenzhen City, just across the border with Hong Long.
Ambassador Liu Xiaoming said at a press conference in London that if the situation deteriorated in the region, but Chinese territory operating under a different system than China, she would act for " to calm the troubles ".
It came after months of anti-Chinese protests that resulted in recent days in the closing of the airport, one of the busiest in the world.
Xiaoming told reporters: "If the situation degenerates into uncontrollable disorder, the central government will not remain by its side, we will have enough power to calm them down.
"We have enough solutions and powers within the limits of the Basic Law to quickly quell any unrest, their actions are serious and violent crimes and already show signs of terrorism.
"The central government of China will never allow some violent offenders to lead Hong Kong into a dangerous path, into a dangerous abyss."
Agency-published footage showed dozens of trucks and armored personnel carriers as well as hundreds of soldiers massing outside the Shenzhen Bay Stadium on the border with Hong Kong in the province. from Guangdong, south of China.
The stadium is right in front of a bridge which is one of the main access roads between the mainland and Hong Kong.
Mr. Liu also focused on Britain, saying that some British politicians still consider Hong Kong to be part of the British Empire.
"The good relations between the United Kingdom and China must be based on the absence of interference by the United Kingdom in China's internal affairs."
Pro-Beijing Hong Kong Chief Executive Officer Carrie Lam warned earlier that the region was in a "state of chaos" and could enter the "abyss".
Sky News reported Tuesday that the protesters stopped the departures at the international airportin the middle of violent clashes with two people accused of supporting Beijing.
Mass demonstrations have been taking place on the territory since June, originally against a bill that would have extradited people to the mainland.
Some involved hundreds of thousands of people and many resulted in clashes between protesters and the police.
Mr. Liu added that it was about extremists posing as democracy protesters hanging around Hong Kong "on a dangerous path".
"We hope it will end in an orderly manner," he said. "In the meantime, we are fully prepared for the worst."
Earlier, US President Donald Trump suggested that trade talks with China could wait until tensions in Hong Kong have eased.
He tweeted: "Of course, China wants to reach an agreement, let them work humanly with Hong Kong first!"
In praising Chinese President Xi Jinping as a "great leader," he added, "I have no doubt that if President Xi wants to solve the Hong Kong problem quickly and humanly, he can do it. Personal meeting? "
Mr. Liu seemed to respond by saying, "Foreign forces must stop interfering in the affairs of Hong Kong, stop conniving in violent crime cases – they must not judge the situation badly and they must not stop. engage in the wrong way, otherwise they will raise the stone before dropping it alone.
"The evidence shows that the situation would not have deteriorated so much without the intervention and the encouragement of foreign forces.
"Hong Kong is part of China, no foreign country should interfere in the internal affairs of Hong Kong."
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