Police once again clashed with street occupiers early Sunday in Mong Kok, a Hong Kong neighborhood that has become the flash point of the city’s ongoing protests.

It was a relatively calm night Saturday until just after midnight, when hundreds of police engaged in what appeared to be another effort to either clear streets of young protesters or at least take back some territory they had recently claimed.

Early Friday morning, police had opened major streets to traffic in Mong Kok, a section of Hong Kong on the Kowloon side of the city that’s popular with mainland Chinese tourists. But later that night, the police were overwhelmed by thousands of protesters seeking to regain their turf, many of them chanting in Cantonese: “Keep going! Keep going!”

After police retreated early Saturday, protesters installed barricades to reclaim and even expand the territory they had lost, although it was not entirely clear that was the reason the police again responded with force.

In a repeat of the previous night, police used pepper spray and clubs on protesters Saturday and early Sunday. Video and firsthand reports suggested that many were injured. Authorities reported that more than 60 police and protesters were injured the previous night, a number that street activists said was far higher.

The continued clashes followed a day in which the government and protest leaders agreed on a time and place to start negotiations. As of Saturday, talks were scheduled to start Tuesday afternoon, involving key student leaders and Carrie Lam Cheng Yuet-ngor, the No. 2 official in the Hong Kong government.

Before the late-night violence, Hong Kong’s police commissioner, Andy Tsang Wai-hung, went public and condemned the ongoing protests, his first comments since his officers used tear gas on protesters on Sept. 28.

“The police have been extremely tolerant of the unlawful acts of the demonstrators in the past two to three weeks,” said Tsang, according to a translation provided by the South China Morning Post. “We did this in the hope that they can calm down and express their views in an otherwise peaceful, rational and lawful manner. Unfortunately these protesters chose to carry on with their unlawful acts . . . which are even more radical or violent.”

Some pro-democracy activists, however, say police are needlessly provoking demonstrators engaged in civil disobedience, making it harder to find a resolution. One of these, Chan Kin-man, a college professor, criticized officers for using pepper spray on young people Friday and Saturday even when police safety was not at risk.

“Many Hong Kongers are saddened by what happened in Mong Kok,” Chan said Saturday. “We don’t want policemen and young people to get hurt because this is not a public order problem, it’s a political problem. . . . It’s a problem with the government’s response and should be solved by political means.”

Protesters in Hong Kong are seeking a more open system for electing the city’s chief executive in 2017. Beijing, which controls Hong Kong, has insisted that candidates for office be screened and approved by a committee it controls. Protesters have labeled that “fake democracy.”

Although united by a common goal, the protesters are splintered, with young people and Mong Kok residents more determined to keep the occupations going than older and wealthier pro-democracy activists.

Hong Kong’s political fault line with Beijing

The divisions have complicated the task of negotiating with the Hong Kong government, which itself is rapidly losing credibility with citizens, even those who oppose the protesters’ tactics.

Chan, the academic and leader of the Occupy Central movement, published a commentary Saturday in Hong Kong’s Ming Pao newspaper urging younger protesters to be more reasonable.

“Let’s think: are we falling into the trap of those who wanted to suppress the movement with public discontent?” he wrote. “In the face of vigorous offensives, would we lose control and respond with violence? If we do, the moral foundation of the whole movement would collapse.”

Chan’s Occupy Central group had planned an occupation of the city’s central business district that would last three days. After the police used tear gas, groups of younger protesters have occupied three sites of the city. Those occupations have since continued — ebbing, rebelling and drawing counterprotests — for three weeks.