US intelligence has confirmed that China is moving troops to the border with Hong Kong, US President Donald Trump said Tuesday, appealing for calm amid intensifying pro-democracy protests in the semi-autonomous financial hub.

Trump relayed the intelligence report in a tweet as protesters paralyzed Hong Kong airport for a second day in defiance of the city’s leaders.

“Our Intelligence has informed us that the Chinese Government is moving troops to the Border with Hong Kong. Everyone should be calm and safe!” Trump said in a tweet.

Chinese state and social media had earlier aired video of security forces gathering across the border from the enclave, which has been rocked by unrest for ten weeks.

The Global Times and the People’s Daily ran a minute-long video compiling clips of armored personnel carriers and troop carriers purportedly driving to Shenzhen, which borders Hong Kong.

The video shows roughly two dozen armored carriers apparently driving through the southern city of Guangzhou and other troop carriers leaving eastern Fujian province.

Hu Xijin, editor-in-chief of the state-run Global Times, said on social media that the military presence is a sign that if the situation in Hong Kong doesn’t improve, China will intervene.

Speaking to reporters in Morristown, New Jersey, Trump called the situation in Hong Kong “very tricky.”

“I hope it works out peacefully, nobody gets hurt, nobody gets killed,” he said.