"The government always tells us 'don't do this and don't do that'. We also want to tell the government 'don't do any policy we don't like'. But she didn't listen," he said of Lam.

The latest protest follows weeks of unrest that have seen millions of people from all walks of life clog streets in the Asian finance hub, posing the greatest popular challenge to Chinese leader Xi Jinping since he came to power in 2012.

Hong Kong returned to Chinese rule in 1997 and has since been governed under a "one country, two systems" formula that allows freedoms not enjoyed in mainland China, including freedom of protest and a much-cherished independent judiciary.

Opponents of the extradition bill see it as a threat to the rule of law and fear it would put them at the mercy of China's justice system where human rights are not guaranteed.

Lam suspended the bill two weeks ago, saying she had heard the people "loud and clear", but opponents say nothing less than the full withdrawal is acceptable.

On Friday night, the ranks of protesters grew steadily as supporters made their way down town after work, just three days before the 22nd anniversary of the handover when another huge protest is expected.

In China, censors have erased or blocked most news of the protests amid concerns that any large public rallies could inspire demonstrations on the mainland.

Joey Siu, with the student union at City University of Hong Kong, said student representatives had travelled to Japan to draw attention to Hong Kong as leaders convene in Osaka for the G20.

"We want to put the agenda there up high. We won't stop saying it simply because Xi Jinping doesn't allow the international community to talk about it in G20," she said.

"We are confident that the world leaders will talk about the situation in Hong Kong."

Xi met with US President Donald Trump on Saturday.

In the latest push for attention, activists took out full-page advertisements in several international newspapers to appeal to the G20 leaders. The appeal was financed by a crowdfunding campaign that raised around HK$5.5 million ($1 million).

On Wednesday, thousands marched to major foreign consulates in the city, urging G20 leaders to back their demand to scrap the bill and "liberate" Hong Kong.

Reuters