US President Donald Trump has signed an order to end preferential treatment for Hong Kong, as his administration adopts an increasingly tough stance on China.

"Hong Kong will now be treated the same as mainland China," the president told reporters at the White House.

Mr Trump said he had also signed bipartisan legislation to impose sanctions on Chinese officials who crack down on rights in Hong Kong.

The US has been paring back Hong Kong's special status over the last few weeks.

"No special privileges, no special economic treatment and no export of sensitive technology," Mr Trump said in Tuesday's announcement from the White House.

The territory, a former British colony, enjoys unique freedoms not seen in mainland China.

But many people there see a new security law imposed by Beijing as bringing an end to Hong Kong's special status, agreed under a 1984 agreement between China and the UK.

The legislation - which outlaws criticism of China's government - is the most sweeping change to the political landscape of Hong Kong since it was handed back to China by the UK in 1997.