Police in Hong Kong fired rubber bullets and tear gas at protesters staging a major pro-democracy march and unidentified masked men attacked commuters with wooden sticks as unrest in the city continued on Sunday.

Footage posted on social media showed masked assailants attacking commuters in a subway station in Yuen Long. Among those attacked were protesters clad in their trademark black clothing and yellow hard hats.

The attackers, meanwhile, were dressed in white with black masks pulled over their heads. On Saturday, demonstrators wore white at a counter-rally in support of police.

The Hong Kong government said in a statement shortly after midnight that commuters had been attacked at a subway station in the city's Yuen Long neighbourhood, with local media reporting that around 30 people were injured.

The statement also said that "some radical protesters initiated a series of violent acts ... despite repeated warnings" by the police. They said the acts included the hurling of petrol bombs, setting fires and throwing bricks.

Aftermath of protesters storming Hong Kong government HQ: In pictures Show all 15 1 /15 Aftermath of protesters storming Hong Kong government HQ: In pictures Aftermath of protesters storming Hong Kong government HQ: In pictures The lobby of the Legislative Council building in Hong Kong is seen covered in graffiti after it was stormed by protesters Getty Aftermath of protesters storming Hong Kong government HQ: In pictures Police officers stand guard at the Legislative Council building in Hong Kong after it was stormed by protesters EPA Aftermath of protesters storming Hong Kong government HQ: In pictures The colonial flag of Hong Kong hangs in the chamber of the Legislative Council after protesters stormed the building Reuters Aftermath of protesters storming Hong Kong government HQ: In pictures Police officers are seen behind cracked glass panels that were damaged by protesters trying to ram their way into the Legislative Council building EPA Aftermath of protesters storming Hong Kong government HQ: In pictures Shattered glass is seen on the outside wall of the Legislative Council of Hong Kong after protesters smashed their way in the building AP Aftermath of protesters storming Hong Kong government HQ: In pictures Riot police patrol the Legislative Council building in Hong Kong after it was stormed by protesters Getty Aftermath of protesters storming Hong Kong government HQ: In pictures Police officers inspect damage to the Legislative Council building in Hong Kong after it was stormed by protesters AFP/Getty Aftermath of protesters storming Hong Kong government HQ: In pictures A caricature of Hong Kong leader Carrie Lam is pasted on a pillar outside of the Legislative Council after protesters broke into the building Reuters Aftermath of protesters storming Hong Kong government HQ: In pictures Graffiti is seen in the chamber of the Legislative Council in Hong Kong after protesters stormed the building Getty Aftermath of protesters storming Hong Kong government HQ: In pictures Abandoned placards and litter is seen outside the Legislative Council building in Hong Kong after a protest on July 1 EPA Aftermath of protesters storming Hong Kong government HQ: In pictures A painting hung i the Legislative Council in Hong Kong is covered in graffiti after protesters stormed the building Getty Aftermath of protesters storming Hong Kong government HQ: In pictures A lift in the Legislative Council building is seen covered in graffiti and litter after protesters stormed the building Getty Aftermath of protesters storming Hong Kong government HQ: In pictures The chamber of the Legislative Council in Hong Kong after protesters stormed the building Getty Aftermath of protesters storming Hong Kong government HQ: In pictures A desk in the chamber of the Legislative Council in Hong Kong is covered in graffiti after protesters stormed the building AFP/Getty Aftermath of protesters storming Hong Kong government HQ: In pictures An area inside the Legislative Council building complex is strewn with litter and smashed glass after it was stormed by protesters Getty

"This is absolutely unacceptable to Hong Kong as a society that observes the rule of law," the statement said, referring to the acts of the subway attackers as well as the protesters.

Earlier in the day, demonstrators hurled eggs and sprayed graffiti at the Liaison Office, which represents China's Communist Party-led central government within the city, as hundreds of thousands took to the streets.

Men in white T-shirts with poles are seen in Yuen Long after attacking anti-extradition bill demonstrators at a train station (Reuters)

Some members of the large crowd, which had defied police orders to end the procession in the Wan Chai commercial district, sprayed surveillance cameras and splattered a Chinese national emblem with black paint.

As hundreds of riot police took up positions nearby, protesters daubed graffiti on massive concrete pillars reading: “Restore Hong Kong, Revolution of Time”.

When asked if the demonstrators would attempt to force entry into the building, one 30-year-old man dressed head to toe in black replied: “No.” Mimicking a throat-slitting action, he said: “That would be the death of Hong Kong.”

Riot police move in against anti-extradition bill protesters on Connaught Road West in Hong Kong (EPA/JEROME FAVRE)

The march had begun peacefully at a public park with protesters repeating their manifesto demands, including direct voting rights for all Hong Kong residents and dissolution of the Legislative Council.

Chanting “Free Hong Kong! Democracy now!”, they also called for an independent inquiry into police brutality during previous protests and the dropping of all criminal charges.

“I think the government has never responded to our demands,” said Karen Yu, a 52-year-old Hong Kong resident.

“No matter how much the government can do, at least it should come out and respond to us directly.”

Police move forward through tear gas as they clash with protesters (Chris McGrath/Getty) (Chris McGrath/Getty Images)

Organisers claimed 430,000 people took part in the demonstration at its peak, while police estimated around 138,000.

Large demonstrations began early last month in opposition to a contentious extradition bill that would have allowed Hong Kong residents to stand trial in mainland China.

Hong Kong’s leader, Carrie Lam, has declared the bill dead but has not formally withdrawn the legislation and some are calling for her to resign amid growing concerns about the steady erosion of civil rights.

Police fire tear gas on protesters to disperse them after the march (LAUREL CHOR/AFP/Getty) (LAUREL CHOR/AFP/Getty Images)

While mostly peaceful, some demonstrations have led to violent confrontations between police and protesters. Activists stormed the Legislative Council building on 1 July and last weekend a fight broke out involving umbrellas and bats inside a luxury shopping centre.

Police officers have also used pepper spray, tear gas, bean bag rounds and rubber bullets in an attempt to control the crowds.

On Friday, homemade explosives were discovered during a raid on a commercial building. Local media reported that protests leaflets were also found but police said no concrete link with the demonstrations had been established.