Embattled Hong Kong leader Carrie Lam will address the city on Tuesday after some of the biggest and most violent protests seen in the financial hub against an extradition bill that she postponed in a stark reversal of policy.

The bill would allow a case by case extraditions to mainland China and despite its postponement, around two million people spilled on to the streets on Sunday, demanding Lam step down and scrap the bill entirely.

Lam's climbdown, with the approval of China's Communist Party leaders, was the biggest policy reversal since the former British colony returned to Chinese rule in 1997 and presented a new challenge for Chinese President Xi Jinping who has ruled with an iron fist since taking power in 2012.

Many accuse China, where the courts are strictly controlled by the Communist Party, of extensive meddling since the handover, with the extradition proposals a further example.

Lam hasn't appeared publicly since the Sunday protests that were the largest in the city for decades.

Since the proposed amendments to the Fugitives Offenders' Ordinance was first put to the legislature in February, Lam has repeatedly rebuffed concerns voiced in many quarters, including business groups, lawyers, judges, and foreign governments against the bill.

Critics say the bill would undermine Hong Kong's rule of law, guaranteed by the "one country, two systems" formula, under which Hong Kong returned to China, by extending China's reach into the city, and allow individuals to be arbitrarily sent back to China where they couldn't be guaranteed a fair trial.

Lam issued an apology on Sunday night through a written government statement that many people said lacked sincerity. It failed to pacify many marchers who said they no longer trusted her and doubted her ability to govern.

Lam, a career civil-servant known as "the fighter" for her straight-shooting and tough leadership style, took office two years ago pledging to heal a divided society. Some observers say she is unlikely to step down immediately but any longer-term political ambitions she may have harboured are now all but dead.

Many protest organisers say they will continue to hold street demonstrations until Lam scraps the bill, fearing that authorities may seek to revive the legislation in future when the public mood is calmer.