One of Hong Kong's most prominent pro-democracy leaders struggled to contain his emotions Wednesday as he warned protests would spread like "blossoming flowers" and pleaded with residents to understand why the city has been brought to a standstill.

Occupy Central co-founder Chan Kin-man told reporters it was inevitable the protests, which have already taken over several main roads and intersections, would grow if the government maintained its hardline stance.

"We understand why citizens are continuing to expand the occupation, it is because the government is so cold," Chan said, regularly having to stop speaking to compose himself.

"Despite such a large occupation, the government is still using such an attitude, so a lot of people think that the action now is not enough and that flowers must continue to blossom everywhere."

Occupy Central is one of the main organisers of the protest which spread to different parts of the semi-autonomous city after riot police tear-gassed demonstrators on Sunday, prompting more supporters to join them on the streets.

Tens of thousands of protesters have assembled in three major commercial and retail areas of Hong Kong for the past three days.

By midday Wednesday, crowds in the central district of Admiralty had already increased to several thousand, with offices closed for a public holiday to mark China's National Day.

Chan, who was close to tears, apologised to citizens for the inconvenience the sit-ins have caused and asked for tolerance.

"I hope everyone will understand what we are doing is not to harm Hong Kong.

"With this short-term inconvenience, we hope to bring about a system that is more fair."

Earlier Wednesday Hong Kong's leader Leung Chun-ying said the community should work together in a "peaceful, lawful, rational and pragmatic manner" while reiterating his commitment to the "Chinese dream".

The city's chief executive has asked protesters to end the sit-in, but his request has had no impact on demonstrators.

The most intense civil unrest Hong Kong has experienced since its 1997 handover from British rule was sparked by Beijing's decision in August to restrict who can stand for the city's top post in elections in 2017.

Protesters have two demands -- that Leung step down and Beijing rescind its insistence that his successor be vetted.