Dissident Chinese artist Ai Weiwei has hit out at United States President Donald Trump, saying clashes between protesters and police in Hong Kong have gotten worse since he indicated the US would not step in to support pro-democracy demonstrators.

Mr Trump last week described the protests, which have entered their 10th week and claimed several lives, as “riots” that China will “have to deal with” itself.

The unrest is the most serious political crisis Hong Kong has seen since it returned to China in 1997, and represents one of the biggest popular challenges to Chinese leader Xi Jinping’s reign since he came to power in 2012.

AAP

The US should be using its significance global influence to support free speech, Mr Ai said.

"You can sense the change in their tactics from the authorities, they've become more brutal after Mr Trump clearly says that's an issue between Hong Kong and China, he's not going to interfere, which is a very bad signal,” he said.

“The United States should be supporting freedom and democracy, and freedom of speech.

“For a major power to give that kind of signal to another authoritarian society is very improper, it will cost more lives and more blood."

Millions of people, many of them young, have taken to the streets in the past three months as part of the protests.

Authorities have been accused of using excessive force to deal with them.

Mr Ai has been documenting the demonstrations since they began in June, uploading photos and footage to his Instagram page to try and attract global attention.

"I do feel the young people in Hong Kong are very intelligent, they understand the difficulties of their struggle and they are prepared for a long-range fighting,” he said.

“Hong Kong people will not be the loser, because they are on the right side of history."

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The protests began as opposition to proposed extradition legislation that would allow people to be sent to mainland China for trial in courts controlled by the Communist Party.

Hong Kong’s government has since suspended the bill, but demonstrators want it fully withdrawn.

Demonstrator demands have since broadened to include calls for greater democratic reforms and for Hong Kong leader Carrie Lam to resign.