Pro-democracy protesters in Hong Kong held hands and formed human chains across the city on Tuesday, as they carried their months-long movement and its demands into 2020 with midnight countdown rallies and a massive march planned for New Year's Day.

The financial hub has been battered by more than six months of protests that included huge peaceful marches attended by millions, as well as violent confrontations in which police have fired tear gas and rubber bullets, and protesters responded with flurries of petrol bombs.

In a video message posted on Facebook city leader Carrie Lam said she would "humbly listen to find a way out" for the city, but didn't address protester demands for greater democratic freedoms and police accountability.

Thousands of people joined hands to form human chains that stretched for kilometres (miles) along busy shopping streets and in local neighbourhoods.

They chanted slogans, sang "Glory to Hong Kong" -- a symbolic protest anthem -- and held up posters calling for people to fight for democracy in 2020.

"Thanks to 2019, which tore off the ugly masks of the police and the government and let the people see the truth," said protester Kris, a medic who participated in the human chain activity.

"The movement is kind of like at its bottleneck now. Hopefully a huge turnout at tomorrow's march could bring back people's passion," he added.

In late November, the city's pro-democracy camp scored a landslide victory in a municipal-level vote widely seen as a referendum on the Beijing-backed government's handling of political unrest.

The movement has since become quieter with sporadic clashes.

On New Year's Eve, protesters also rallied at major shopping malls, which have become regular protest venues as participants try to cause economic disruption.

Further protests were planned Tuesday around the city, including on both sides of Victoria Harbour and at nightlife hotspot Lan Kwai Fong.

The city's traditional New Year Eve's bumper fireworks display has been cancelled due to safety concerns, but a light show and smaller-scale fireworks will take place instead.

"2019 is a remarkable and special year for every single Hongkonger," 25-year-old teacher Sam told AFP as he celebrated New Year's Eve with his family at the harbourfront.

"People's demands are loud and clear, but the government is not listening. In 2020, I really hope it will be a better year for all Hong Kong people."

Civil Human Rights Front (CHRF), the chief organiser of the city's record-breaking marches, will kick off the new year with a huge demonstration on Wednesday, urging the government to respond to people's five demands -- which include an independent inquiry into the police, amnesty for arrestees and fully free elections.

Police have arrested nearly 6,500 people since June -- nearly a third aged under 20.

"The youngsters have sacrificed a lot for justice... 2019 is a wake-up call," a 63-year-old retiree who gave his surname as Shiu told AFP.

"People will be more determined in the new year. People know that the future of Hong Kong depends on whether we can achieve the five demands."

The demonstrations were initially sparked by a now-abandoned bill to allow extraditions to the authoritarian mainland, but have since morphed into a popular revolt against Beijing's control -- the biggest crisis since the former British colony's return to Chinese rule in 1997.