The ground-level concourse of the Kwai Fong MTR station was filled with smoke as riot police first fired tear gas into the building at retreating protesters, then stormed inside and opened fire again.

Tear gas was used after multiple warnings and MTR announcements that the station was closed and trains would not be stopping at Kwai Fong, except for additional ones arranged to pick up people already inside.

A man in protest gear was seen lying on the platform, with blood running from his nose, while other protesters were helping him. Video footage also showed a stationary train at a platform with people still inside.

There was more trouble later at Tai Koo station, with riot police charging inside to grab protesters who had been moving from one station to another.

Video footage showed officers at the top of a long, steep escalator beating protesters, while tear gas fumes filled the air.

But with police out in force and protesters staying away from North Point, there were only isolated incidents of Fujianese becoming belligerent and attacking some passers-by and journalists at the scene.

Police fired tear gas at them from inside, and at one point at night, riot officers from the Special Tactical Squad charged out to disperse protesters attacking them from the Park Lane Shopper’s Boulevard, where they had blocked a key thoroughfare – the section of Nathan Road between Austin and Salisbury roads.

The “raptors”, as officers from the squad are known, beat protesters with batons and made several arrests.

A female protester was treated by paramedics at the scene, her face bleeding after she was hit by a beanbag round, according to witnesses. A policeman inside the station suffered burns to his legs after being hit by a petrol bomb.

The clashes intensified at night after a day of confrontations that mostly saw protesters blocking roads and engaging police in stand-offs, only to retreat and strike at the next location when officers fired tear gas or charged at them.

Protesters wearing gas masks and helmets were seen regularly darting across roads to pick up smoking canisters and throw them back at police with well-practised ease.

Sham Shui Po and North Point had been on high alert since morning, with shops closed as the protesters were expected to march in defiance of the police bans.

The crowds gathered at Maple Street Playground in Sham Shui Po and across the harbour at Victoria Park at about 2pm.

Those in Sham Shui Po marched towards Cheung Sha Wan and the local police station at around 3pm, while those at Victoria Park, who had permission only to remain there, headed out to take over roads in Causeway Bay and Wan Chai, throwing traffic into chaos.

One group also went to Golden Bauhinia Square in Wan Chai, and sprayed anti-China slogans on the base of the showpiece statue that is a popular attraction for tourists from mainland China.

Others gathered at the junction between Lockhart Road and Fenwick Street at night, just a block from police headquarters, which was heavily guarded by riot police and protected by water-filled barriers. Police fired tear gas to disperse the protesters, who hurled petrol bombs in their direction.

In Causeway Bay, several protesters complained to the media that they were being arrested by police officers disguised as demonstrators.

Television footage showed several masked men dressed in black working together with uniformed police.

As other battlefields cleared, angry residents gathered in areas such as Shau Kei Wan, Sai Wan Ho and outside Sha Tin Police Station late into the night, expressing their anger at police use of tear gas in heavily populated districts.

Past midnight, the government issued a statement strongly condemning protesters and saying it was outraged by their actions. It urged the public to say “no” to violence and to help restore order.

At about 1am, live news footage showed a group of white-clad men with poles and metal rods beating up some people at Yi Pei Square in Tsuen Wan. Riot police arrived in about 10 minutes, but the mob had fled by then. The video showed shattered glass, a shovel, knives and rods strewn all over the scene.

At Sha Tin Police Station, news footage also showed two men being pinned down by officers. It was not known why they were being subdued. The move enraged onlookers even more, and they shouted abuse at police.

Despite the escalating confrontations, pro-Beijing politicians noted that the number of protesters on the streets appeared to be diminishing in general.

“It has become repetitive, so some of their supporters are tired of that … Police are also making better plans, as it has become meaningless to engage in long stand-offs with smaller groups of protesters,” National People’s Congress (NPC) Standing Committee member Tam Yiu-chung said.

Fellow NPC delegate Maggie Chan Man-ki suggested the wider public was distancing itself from the violence. She said warnings from Beijing and riot charges against those arrested were also having a deterrent effect.

But opposition lawmaker Lam Cheuk-ting of the Democratic Party said public anger was far from over.

Civil rights groups condemned the police’s escalated use of force in MTR stations, saying it almost amounted to retaliation against protesters.

Icarus Wong Ho-yin of Civil Rights Observer said police’s own guidelines, as well as those of arms manufacturers, stated tear gas should only be used in open or well-ventilated areas. “The use of tear gas in Kwai Fong station is definitely not justified,” he said.

Legal scholar Eric Cheung Tat-ming, who used to sit on police watchdog the Independent Police Complaints Council, noted the use of pepper balls from short range at Tai Koo station.

“It can hardly be justified, firing from such a short distance in Tai Koo,” Cheung said. “And that already went beyond the intent of stopping any acts of crime when officers made the arrest in the stations.”

Reporting by Michelle Wong, Kathleen Magramo, Emily Tsang, Phila Siu, Karen Zhang, Sarah Zheng, Josephine Ma, Martin Choi, Meaghan Tobin, Hari Raj and Danny Mok.