China "will not stand idly by" and will retaliate if the US goes ahead with its plans to deploy intermediate-range missiles in the Indo-Pacific.

Singling out Australia, the Chinese foreign ministry's director of arms control, Fu Cong, issued the warning at a press conference in Beijing on Tuesday, the news agency AFP reports.

Watch the latest on the Hong Kong protests in the video above

"We also call on our neighbours, our neighbouring countries, to exercise prudence and not to allow a US deployment of its intermediate-range missiles on (their) territory," Fu said, naming Australia, Japan and South Korea as the neighbours he was referring to.

"That would not serve the national security interest of these countries," he added.

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No formal discussions

Prime Minister Scott Morrison has denied the government is in formal discussions with the Trump administration over constructing US missile bases in Australia, after the US defence secretary Mark Esper suggested on Sunday he was canvassing possible sites in the region.

Chevron Right Icon 'It's not been put to us.'

"It's not been asked of us, not being considered, not been put to us," Morrison said in Brisbane on Monday.

"I think I can rule a line under that."

Beijing's aggressive territorial actions in the South China Sea are causing growing concern from Australia, the US and other Pacific rim countries.

Director of the foreign ministry's Arms Control Department, Fu Cong, speaking at the Beijing press conference on Tuesday. Credit: AP

It is widely rumoured that if the US were to deploy weapons against China in the region, it would use Guam in Micronesia as its launching base.

The US island territory is about 3,000 km from Shanghai on the east coast of China.

Any such action would be viewed as "a very provocative action on the part of the US and it can be very dangerous," said Fu, according to the AFP report.

Crackdown

In a separate display of verbal strong-arming, China's spokesman for Hong Kong affairs, Yang Guang, warned pro-democracy protesters in the restless province that "those who play with fire will perish by it".

Monday saw the most violent day of clashes yet between police and protesters, with more than 140 people arrested.

Chevron Right Icon 'Don't mistake our restraint for weakness.'

Yang warned at Tuesday's press conference in Beijing that "radical protests" had severely impacted Hong Kong's prosperity and stability, "pushing it into a dangerous abyss".

Policemen in riot gears move to disperse residents and protesters at Sham Shui Po district in Hong Kong on Wednesday. Credit: AP

"Don't ever misjudge the situation and mistake our restraint for weakness," Yang warned.

"Don't ever underestimate the firm resolve and immense strength of the central government."

The protests in Hong Kong began two months ago after the city's leader, Carrie Lam, attempted to introduce a law that would have allowed residents to be extradited to mainland China to face trial.

The bill has since been suspended but the protests have continued with demands for further democratic reform.