Alarmed by the troop build-up, the US has urged Beijing to respond with restraint to more than 10 weeks of violent clashes between pro-democracy demonstrators and police in Hong Kong, which is ruled by China but enjoys a large degree of autonomy from the mainland.
Video published by the AFP news agency purported to show the start of military drills inside a sports stadium in Shenzhen, just 30km from the city. Large numbers of soldiers could be seen marching across a grass pitch in the stadium flanked by armoured personnel carriers.
Chinese state media released their own video earlier this week showing troops arriving at the stadium ahead of “apparent large-scale exercises”, in what appeared to be a show of force directed at the protest movement.
In tweets, Mr Trump urged China to deal with Hong Kong “humanely”, suggesting that any trade talks could wait until the tensions have eased.
He praised Mr Xi, calling him a "great leader" and saying he could quickly resolve the unrest in Hong Kong if he wanted to. "I have ZERO doubt that if President Xi wants to quickly and humanely solve the Hong Kong problem, he can do it. Personal meeting?" Mr Trump tweeted.
The US president has previously said little about the crisis beyond urging both sides to express caution, although some American politicians have come out with stronger statements.
Last week, House Speaker Nancy Pelosi issued a statement saying that "dreams of freedom, justice and democracy can never be extinguished by injustice and intimidation."
But the US State Department said it was deeply concerned about reports that Chinese forces were gathering near the border and urged the city's government to respect freedom of speech.
Protests continued on Wednesday night and are expected to resume with greater intensity at the weekend. Demonstrations which started in defiance of a new extradition law have spilled over into general unrest at the perceived loss of the city’s autonomy to the mainland.
Police and protesters again faced off on the streets, with riot officers quickly firing tear gas as their response to demonstrators hardens.
The clashes did not impact the city’s international airport, however, after unrest inside the terminal forced cancellation of nearly 1,000 flights earlier this week.
The airport’s management have since increased security, and said that normal operations would resume on Thursday.
Several protests were planned across different districts of Hong Kong from Thursday, including a teachers rally, and one gathering at a government building in the popular Wan Chai bar district.
The Civil Human Rights Front, which organised million-strong marches in June, set another protest for Sunday, while an organise of animal lovers is set to mobilise - upset at their pets being tear-gassed.
The movement continues to push for authorities to listen to their set of five demands, including the resignation of chief executive Carrie Lam and the complete withdrawal of the extradition bill, but it remains to be seen whether the intensifying violence has eroded their public support.
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