Hong Kong's leader Thursday urged pro-democracy protesters to end their demonstrations after her surprise decision to bow to one of their key demands was condemned as too little, too late.

Carrie Lam, the city's pro-Beijing chief executive, surprised many on Wednesday when after three months of rallies she suddenly announced she was scrapping a hugely unpopular extradition law.

Millions of people have taken to Hong Kong's streets since June in the biggest challenge to China's rule of semi-autonomous Hong Kong since its handover from the British in 1997.

The protests were sparked by a proposed bill allowing extraditions to the authoritarian mainland but as Beijing and Lam refused to budge the movement morphed into a broader campaign calling for democratic reforms and police accountability.

On Wednesday evening Lam released a video message saying she was scrapping the bill entirely, a key demand of protesters.

At a press conference on Thursday, Lam continued her newfound conciliatory tone, saying her decision to fully withdraw the bill was an attempt "to help prevent violence and stop chaos as soon as possible, resume the social order and help our economy and people's livelihood to move forward".

"It is obvious to many of us that the discontentment in society extends far beyond the bill," she added, saying she recognised that anger over inequality and the government had spiralled and needed to be solved.

She renewed her appeal for protesters to enter into a dialogue with her administration and called on moderate protesters to abandon their more militant allies who have frequently clashed with riot police over the last 14 weeks.

But there is little sign her belated concession will end protests of heal divisions in the international financial hub.