HONG KONG — Hundreds of thousands of people packed Hong Kong streets for an annual New Year’s Day protest march as the monthslong pro-democracy movement extended into 2020 with further violence between police and demonstrators.

Police said they arrested about 400 people for unlawful assembly and carrying offensive weapons as black-clad youths broke off from the main group of marchers and attacked banks and ATM machines with spray paint, hammers and Motolov cocktails. They smashed crossing lights, ripped bricks from sidewalks and barricaded roads in the downtown financial district.

Banks and businesses identified with mainland China have been frequent targets of some protesters.

Police used pepper spray, tear gas and a water cannon to drive off the demonstrators, although a government statement said officers were “deploying the minimum necessary force.”

Senior Superintendent Ng Lok-chun told reporters that “rioters” hijacked the protest march and at one point endangered police officers by surrounding and throwing objects at them, which led to police ordering the rally to be called off.

The rally followed overnight clashes between police and protesters on New Year’s Eve in a densely populated shopping district. Police also used tear gas, pepper spray and water cannons to break up groups of demonstrators who blocked traffic and lit fires in the street in the working-class district of Mong Kok.

Hong Kong toned down its New Year’s celebrations amid the protests that began in June.

Eric Lai, the vice convener of the march organizer, the Civil Human Rights Front, said he hoped to avoid a recurrence of the previous night’s violence.

“We hope that the police can facilitate us, rather than provoking us, and to fire tear gas and water cannon at us,” he said.

Such marches have often devolved into violence. Both sides have been accused of provoking clashes, and nearly 6,500 protesters as young as 12 have been arrested in scores of incidents on streets, in shopping malls and on college campuses.

Recent protests have drawn participants from across Hong Kong society, sometimes numbering more than 1 million and packing the downtown area from Victoria Park to the government office complex a short distance away. Many of those joining in are concerned about an erosion of the former British colony’s civil liberties it was promised after being handed over to Chinese rule in 1997, along with a shortage of well-paying jobs and a yawning divide between the city’s ruling class and those merely getting by amid soaring housing costs.

The protests began in June over proposed legislation that could have allowed residents to be extradited to China where they could face possible torture and unfair trials. The legislation was withdrawn, but not before the protests expanded to wider calls for reforms in the semi-autonomous Chinese territory.