Almost 500,000 people in Hong Kong have now signed up for a free mass testing programme that is due to begin on Tuesday.

The scheme comes as the city battles a third surge in infections, weeks after the virus appeared to be largely under control.

But the involvement of a medical team from Beijing in the testing programme has struck fear in some who say it will lead to widespread DNA collection - something authorities have denied.

Pro-democracy activist Joshua Wong called for a boycott, warning of "large-scale DNA collection paving way to China-style surveillance".

China recently imposed a controversial national security law in Hong Kong that many say impedes the city's freedoms.