US senator warns Hong Kong becoming 'police state' as thousands rally

Hong Kong is sliding towards becoming a police state, US senator Josh Hawley warned Monday, as tens of thousands filled the strife-torn city's streets waving American flags and calling on Washington to punish China over sliding freedoms.

The international finance hub was battered by another weekend of unrest as hardcore pro-democracy protesters and police fought running battles with officers warning the violence had now reached "life-threatening levels".

Protests pushing for greater democratic freedoms and police accountability have raged for the last 19 weeks and there is little end in sight as Beijing and local leaders refuse concessions.

On Monday night a huge crowd filled Hong Kong's commercial district to show support for a US bill that could dramatically alter Washington's relationship with the trading hub.

The Hong Kong Human Rights and Democracy Act, which could be discussed and voted on by the House of Representatives as early as this week, would require annual reviews of the territory's special trading status -- and potentially sanction some Chinese officials.

Monday's rally was the largest in weeks partly because it was granted permission to go ahead by police.

"We are here to make an urgent call out to the international community to support us, we have no other way," a 24-year-old art student, who gave her surname as Chun, told AFP.

Among the bill's sponsors is Hawley, a Republican senator for Missouri who was in Hong Kong on a two-day trip during which he watched protests on Sunday.

"The situation here is urgent," he told reporters shortly before flying back to Washington before Monday night's rally.

Asked what his message would be on returning to Congress he replied: "That Hong Kong is in danger of sliding towards a police state and that representative government in Hong Kong is at risk, and that the one country two systems model is at risk."