Thousands dressed in black marched in Hong Kong today to press for the full withdrawal of a controversial extradition bill that has triggered violent protests and plunged the financial hub into a political crisis.

Demonstrators, mostly students wearing hard hats, goggles and face masks, disrupted traffic on key roads in a mostly peaceful protest to demand that embattled leader Carrie Lam, who promoted and then postponed the bill, scrap it altogether.

"We want to fight for our freedom," said high school student Chan Pak-lam, 17, who was protesting in the sweltering heat of about 30°C.

"We want the law to be withdrawn, not suspended. I will stay here until night. If the government doesn't respond, we will come again."

The protests, which pose the greatest popular challenge to Chinese President Xi Jinping since he took power in 2012, once again forced the temporary closure of government offices over security concerns.

Millions have clogged the streets of the Chinese-ruled city this month to rally against the bill, which would allow people to be extradited to the mainland to face trial in courts controlled by the Communist Party.

It triggered the most violent protests in decades when police fired rubber bullets and tear gas to disperse the crowds.

Today's marchers demanded that the government drop all charges against those arrested in last week's clashes, charge police with what they describe as violent action and stop referring to the protests as a riot.

Democracy activist Joshua Wong, who walked free from prison on Monday, urged police chief Stephen Lo to speak to the protesters, while others expressed anger at how some police have treated the demonstrators.

"Sincere Attitude"

"We are mad at how they treat the protesters," said Democratic lawmaker Ted Hui Chi-fung.

The bill’s suspension has done little to pacify opponents, who fear the law could put them at the mercy of the mainland Chinese justice system which is plagued by torture, forced confessions and arbitrary detentions.

The turmoil has also raised questions over Lam's ability to govern, two years after she was selected and pledged to "unite and move forward".

Fears of China meddling

Since it returned to Chinese rule in 1997, the former British colony has been governed under a "one country, two systems" formula that allows freedoms not enjoyed in mainland China, including a much-cherished independent judiciary.

But many accuse China of obstructing democratic reforms, interfering with elections and of being behind the disappearance of five Hong Kong-based booksellers, starting in 2015, who specialised in works critical of Chinese leaders.

While Lam admitted shortcomings over the bill and said she had heard the people "loud and clear", she has rejected repeated calls to step down.

Concerns over the bill spread quickly, from democratic and human rights groups to the wider community, including pro-establishment business figures, some usually loath to contradict the government.

Some Hong Kong tycoons have started moving personal wealth offshore.

"Don't give up"

Protesters had gathered early today outside government offices before marching towards the police headquarters. One activist read a letter of support from a Taiwan student.

"Brave HKers, perhaps when faced with adversity, we are all fragile and small, but please do not give up defending everything that you love," the protester read through a loud hailer, to applause from the crowd.

After promises that post-handover Hong Kong should enjoy a high degree of autonomy, Beijing's squeeze has fuelled widespread resentment and in 2014 sparked pro-democracy protests that paralysed parts of the city for 79 days.

- Reuters