Satellite photos show what appear to be Chinese armoured personnel carriers and other military vehicles across the border from Hong Kong.
Parked in a sports complex in the city of Shenzhen, the deployment has been interpreted as a threat from Beijing to use increased force against pro-democracy protesters.
The pictures, collected on Monday by Maxar's WorldView, show 500 or more vehicles sitting on and around the soccer stadium at the Shenzhen Bay Sports Centre.
The military force is just across the harbour from the Asian financial hub that has been rocked by near-daily street demonstrations.
Hong Kong's 10-week political crisis, in which millions of people have taken to the streets calling for a halt to sliding freedoms, is the biggest challenge to Chinese rule of the semi-autonomous city since its 1997 handover from Britain.
According to CCN, the paramilitary troops are part of the People's Armed Police Force.
An official said China had the capability to put significant forces into Hong Kong "within several hours".
So far there is no indication that China's military has intervened directly in the Hong Kong crisis.
The images were released just two days after the Chinese Government published footage that appeared to show military vehicles driving towards the Hong Kong border.
The short clip shows a series of roughly two dozen green armoured fighting vehicles entering a "service area" in a row and riding down a highway, purportedly towards Shenzhen, the mainland city bordering the territory.
The state-run People's Daily did not comment on the purpose of the vehicles but noted that the People's Armed Police was in charge of "handling riots, turmoil, seriously violent, criminal activities, terrorist attacks and other societal security incidents".
Last week, Chinese police in Shenzhen carried out a large-scale anti-riot drill involving 12,000 officers in which they demonstrated a newly developed teargas to quell protesters.
At the start of August, Chinese forces congregated abruptly at the border with Hong Kong, alarming the White House.
Beijing appears to be losing patience after 10 weeks of protests.
China's official Xinhua news agency published an editorial saying "ugly forces" were threatening the country's "bottom line".
Those "ugly forces" are Hong Kong's pro-democracy protesters.
"The central government will not sit idly by and let this situation continue," the agency wrote, as China's military repeated assertions that it is ready to quell the "intolerable" unrest if ordered.
Analysts have warned any move by China to intervene militarily in Hong Kong will backfire.
"Even 100 soldiers in the central business district, if they suddenly appeared on the front page of all major newspapers, would have a very chilling impact on multinational companies based in Hong Kong," Willy Lam, adjunct professor at the Chinese University of Hong Kong told CNN.