US National Security Adviser John Bolton warned China not to create a "new" Tiananmen Square in response to the pro-democracy protests in Hong Kong.

"The Chinese should study very carefully the steps they are taking, because the Americans remember Tiananmen Square and remember the image of the man standing in front of the column of tanks," Bolton said.

Chinese forces violently suppressed the protesters in Tiananmen Square in 1989, and the image of the man standing in front of a column of tanks is still fresh.

"It would be wrong to create new memories like that, in Hong Kong," Bolton said.

Trump proposes
US President Donald Trump has suggested that Chinese President Xi Jinping hold a meeting with pro-democracy activists in Hong Kong.

"If President Xi meets directly and personally with the protesters, there will be a happy ending to the Hong Kong problem, I have no doubt about it," Trump wrote on his Twitter account.

Trump has been reluctant to criticize China's stance on Hong Kong, saying he views the unrest as an internal affair of Beijing and focused on negotiations to resolve the US-China trade war.

Military moves
Meanwhile, the Agence France-Presse said a Chinese military force was seen Thursday morning near the border with Hong Kong.

Thousands of Chinese military police at a sports stadium in Shenzhen, a city bordering Hong Kong (Reuters)

According to Agence France-Presse, thousands of Chinese military police gathered at a sports stadium in Shenzhen, a city bordering Hong Kong, and trucks and armored vehicles participated in exercises to transport them there.

Chinese state media also released videos of military convoys heading for Shenzhen.

Al-Jazeera correspondent said the observers ruled out Chinese military intervention, as Beijing is calculating the tension that might lead to it with major powers.

The clashes between police and demonstrators on the streets of Hong Kong were renewed yesterday, as police dispersed protest gatherings using tear gas.