Hong Kong demonstrators gather at airport

Demonstrators have gathered at Hong Kong's airport, marking the start of three days of unauthorised rallies in the Chinese territory.

The move is the latest challenge to the government's apparent strategy of waiting out the ongoing political crisis and comes just days after a citywide strike shut down flights and trains causing travel chaos.

Protesters held signs in English and Chinese and had printed leaflets in multiple different languages explaining the causes and demands of the demonstrations for arriving tourists.

Activists dressed in black sat in the arrivals hall waving banners to raise awareness among international visitors.

Protests have gripped Hong Kong for weeks, beginning with anger at an extradition bill and morphing into demands for greater freedoms.

The former British colony is part of China but enjoys more autonomy.

It has a free press and judicial independence under the "one country, two systems" approach - freedoms activists fear are being increasingly eroded.

The protesters have called for an independent inquiry into alleged police brutality during the protests, the complete withdrawal of the controversial extradition bill, and the resignation of Hong Kong's leader Carrie Lam.

Beijing has warned demonstrators not to "play with fire" or to "underestimate the firm resolve [of] the central government".

Demonstrators plan to stay at the airport throughout the weekend.

Hong Kong's airport is one of the busiest in the world, handling 1,100 passenger and cargo flights daily, with services between the city and about 200 international destinations.