WASHINGTON — The US Senate unanimously adopted legislation on Tuesday supporting "human rights and democracy" in Hong Kong and threatening to revoke its special economic status, prompting China to angrily threaten countermeasures.

The lawmakers also approved a measure that would ban the sale of tear gas, rubber bullets and other equipment that have been used by security forces to suppress protests for nearly six months.

The Senate's Hong Kong Human Rights and Democracy Act would require the US president to annually review the favorable trade status that Washington grants to Hong Kong.

It also mandates sanctions against Hong Kong and Chinese officials who commit human rights abuses including "extrajudicial rendition."

The Senate Foreign Relations Committee's top Democrat, Robert Menendez, said that the legislation "makes it clear that the US will stand firmly and unambiguously with the legitimate aspirations of the people of Hong Kong."

The movement was ignited in June when millions took to streets in opposition to a now-abandoned attempt to allow extraditions from Hong Kong to the mainland.

The protests and resulting crackdowns have turned parts of Hong Kong into violent battlegrounds for weeks.

On Tuesday protesters occupying a university defied warnings to surrender, as skirmishes between police and demonstrators continued.

The Senate bill updates the original Hong Kong Policy Act of 1992.

The House and Senate will now harmonise the texts into a single bill to pass Congress and go to President Donald Trump's desk for his signature. — AFP