Hong Kong police clashed with students, using pepper spray and making 45 arrests as they continued to clear barricades around protest sites early on Wednesday, appearing to gain the upper hand in the standoff for the first time since pro-democracy protests began last month.

On Tuesday morning, police officers using chain saws and sledgehammers had cleared away the barricades near two protest sites and reopened several major roads in Hong Kong, in well-planned and peaceful operations that helped ease much of the traffic congestion the sit-in had caused.

But less than 24 hours later, there were dramatic and angry scenes as hundreds of police, some in riot gear, charged through a tunnel the protesters had blocked, ripping up barricades, using pepper spray and arresting 37 men and eight women who refused to get out of the way.

The stakes had been raised that evening when a group of protesters made an attempt to extend the protest site by blocking a road tunnel running alongside Hong Kong’s Legislative Council building, the territory’s mini-parliament.

In the process, masked demonstrators, some wearing construction helmets, had advanced on a group of around a dozen police officers in the Lung Wo Road tunnel, some demonstrators carrying umbrellas and some with their hands in the air.

Police officers remove an umbrella fixed to the barriers that protesters set up to block off main roads in central Hong Kong. (Kin Cheung/AP)

One police officer held up a large red sign warning protesters to “stop charging or we use force,” but the officers soon found themselves surrounded in the tunnel, and were forced to withdraw, allowing protesters to build new barriers with concrete slabs.

Police said four of their officers had been hurt in Lung Wo Road, including one who suffered a dislocated shoulder and another who was cut near his eye after being poked with an umbrella.

In a statement, police condemned the protesters for endangering people’s safety. “Protesters advancing against police cordon line even with their arms raised is not a peaceful act,” the statement said.

The police response took only a matter of hours, clearing the tunnel again in a show of force.

“The police were mad at us for blocking Lung Wo Road, and they were a little bit aggressive,” said 29-year-old teacher Cheung Mai-lai.

Nearby, protesters cursed the police from behind the next set of barricades and accused them of defending the government and not the people.

The attempt to extend the protest site divided opinion among the protesters, with some arguing that it was unnecessarily provocative and could cost them public support. The lack of strong leadership among the movement was never more apparent.

“Our movement is not really about grabbing land,” Cheung added. “But some people don’t want to give up what we have already achieved.”

The student-led protests have been extremely peaceful up until now, but there was a more aggressive edge to the mood among some people on Tuesday.

It was fueled by a sense of powerlessness after hundreds of police descended first on the Causeway Bay shopping area and then on Queensway, a wide road running through the heart of Hong Kong’s business district. Meanwhile, the government still has not offered the protesters any concessions.

Police left untouched the main protest area on Harcourt Road, just north of Queensway in Admiralty District, while some protesters continued to occupy one side of the road in Causeway Bay. But the police action allowed trams, buses and taxis to operate much more freely on Hong Kong Island.

By lunchtime, traffic was flowing freely down Queensway for the first time in more than two weeks, while police remained on the sidewalks to keep demonstrators at bay.

“I am angry because teenagers took so long building up the barricades but the police removed them so quickly,” said Pomi Chow, 24, who said she had come from her job as a secretary to defend the protest site but would go home to sleep.

Meanwhile, thousands of people continued to mill about at the protest site, studying, reading and chatting calmly. Knots of young men discussed tactics to be used if police attempted to clear the area.

Police had carried out a similar operation to clear barriers on the periphery of the protest sites on Monday. They said more such operations would be carried out in coming days, adding that they would not rule out making arrests “when necessary.”

At the outset of the protests, police had used tear gas and pepper spray on crowds, but the move backfired, bringing thousands more people into the streets. This week’s operations have been much more restrained and more effective, at least until the action to clear Lung Wo Road.

Writing on his blog, Leung Chun-ying, Hong Kong’s chief executive, asked protesters to move to city parks so they did not obstruct traffic.

“For days, the government and police and affected people tolerated to the greatest extent the occupiers voicing their demands, but road-blocking has created long-term effects on people’s daily lives,” he wrote. “Such a situation cannot continue.”

In Beijing, the official People’s Daily Newspaper warned in a commentary that democracy was “no excuse for turmoil” and that protesters’ attempts to force Leung to resign were “doomed to fail.”