Hong Kong riot police have fired tear gas at thousands of protesters, many wearing masks and reindeer horns, after scuffles in shopping malls and in a prime tourist district as anti-government rallies escalated into chaos on Christmas Eve.

Key points: Police fired tear gas to disperse protesters who had occupied the main roads outside the malls

Police fired tear gas to disperse protesters who had occupied the main roads outside the malls Protesters chanted slogans including "Revive Hong Kong, revolution of our time"

Protesters chanted slogans including "Revive Hong Kong, revolution of our time" The Civil Human Rights Front has applied to stage another march on New Year's Day

Protesters inside the malls had thrown umbrellas and other objects at police, who responded by beating some demonstrators with batons and with one officer pointing his gun at the crowd but not firing.

Police fired tear gas to disperse protesters who had occupied the main roads outside the malls and nearby luxury hotels.

There was a heavy police presence into the night in Tsim Sha Tsui with hundreds of officers standing guard on the roads as thousands of Christmas shoppers and tourists, some wearing Santa hats, looked on.

A water canon and several armoured police vehicles were parked nearby.

A man was shown on public broadcaster RTHK falling from the second floor to the first floor of a mall in the rural Yuen Long district as he tried to evade police. He was conscious and taken away by paramedics.

A plainclothes police officer uses pepper spray to disperse anti-government demonstrators inside a shopping mall. ( Reuters: Tyrione Siu )

Dozens of protesters had started digging up bricks from the roads and setting up barricades, as police said in a statement they would deploy "minimum force to effect dispersal" and arrest "rioters".

Metro operator MTR Corp said it shut two stations, Mong Kok and Tsim Sha Tsui, early on Tuesday night (local time) due to protests in the area. Train services were meant to run overnight on Christmas Eve.

Many families with children had congregated in the same area to view the Christmas lights along the promenade in the Tsim Sha Tsui East tourist district of Kowloon, the spectacular backdrop of Hong Kong island on the opposite side of the harbour.

The protests, now in their seventh month, have lost some of the scale and intensity of earlier violent confrontations.

A peaceful rally earlier this month still drew 800,000 people, according to organisers, showing strong support for the movement.

A woman wearing Christmas decorations in her hair reacts to tear gas as police confront protesters on Christmas Eve in Hong Kong. ( AP: Kin Cheung )

Scores of black-clad, mask-wearing protesters chanted slogans including "Revive Hong Kong, revolution of our time," and "Hong Kong independence," as they roamed the malls.

"Lots of people are shopping, so it's a good opportunity to spread the message and tell people what we are fighting for," said student Ken, 18.

"We fight for freedom, we fight for our future."

In a video posted on her Facebook page, Chief Executive Carrie Lam wished Hong Kong citizens "a peaceful and safe Merry Christmas".

Ms Lam has so far refused to grant protesters' demands which include an independent inquiry into police behaviour and the implementation of full universal suffrage.

At one mall in the teeming Mong Kok district, also on the Kowloon peninsula, police used pepper spray to disperse some protesters.

Some protesters were planning to march in Tsim Sha Tsui and count down to Christmas, according to notices on social media.

Around 100 protesters also damaged a Starbucks inside a mall called Mira Place, breaking the glass counters displaying pastries and spraying graffiti on the walls.

The coffee shop chain has been a common target of protesters after the daughter of the founder of Maxim's Caterers, which owns the local franchise, condemned the protesters at a UN human rights council in Geneva.

The Civil Human Rights Front, which has organised some of the biggest marches involving more than a million people, applied to stage another march on New Year's Day.

Police have arrested more than 6,000 people since the protests escalated in June, including a large number during a protracted, violent siege at the Hong Kong Polytechnic University in mid-November.

Many Hong Kong residents are angry at what they see as Beijing's meddling in the freedoms promised to the former British colony when it returned to Chinese rule in 1997.

China denies interfering and says it is committed to the "one country, two systems" formula put in place at that time and has blamed foreign forces for fomenting unrest.

Reuters