A Hong Kong police officer shot at masked protesters on Monday morning, hitting one in the torso, as anger sparked by the recent death of a student spilled into the rush hour commute and wreaked fresh chaos.

The shooting, which was broadcast live on Facebook, is the latest escalation in more than five months of pro-democracy protests that have engulfed the international financial hub and battered its reputation.

Footage showed a police officer drawing his sidearm in the district of Sai Wan Ho as he tried to detain a masked person at a junction that had been blocked by protesters.

Another unarmed masked individual then approached the officer and was shot in the chest area, quickly falling to the ground, clutching their left side.

Seconds later, two more live rounds were fired as the officer scuffled with another masked protester who fell to the ground. Both were detained by officers.

Hong Kong police said live rounds were fired and that one person was struck.

A pool of blood could be seen near the first individual whose body initially appeared limp, although the person was later filmed conscious and even trying to make a run for it.

The second man was conscious, shouting his name to reporters as he was handcuffed.

Hospital authorities said three people were admitted from the incident, one with a gunshot wound.

Hong Kong protest
With no political solution on the table, Hong Kong police officers have been left to battle violent protesters and are now loathed by large chunks of the deeply polarised population. Photo: AFP / Anthony WALLACE

Hong Kong has been upended by 24 consecutive weeks of huge and increasingly violent rallies, but Beijing has refused to give in to a movement calling for greater democratic rights and police accountability.

Tensions have soared following the death on Friday of a 22-year-old student who succumbed to injuries sustained from a fall in the vicinity of a police clearance operation the weekend before.

The city has seen four days of violent protests since Alex Chow's death, as well as tens of thousands attending peaceful mass vigils.

Using online messaging forums, activists had called for a general strike on Monday morning.

Flashmob protests sprung up in multiple districts during the commuter period, with small groups of masked protesters targeting subway stations and building barricades on road junctions.

Hong Kong protest
Hong Kong police shot a protester on Monday in the latest escalation in the city's political crisis. Photo: AFP / Anthony WALLACE

Even before the shooting in Sai Wan Ho, tear gas had been fired in at least two other locations.

One video circulated by protesters on messaging channels from Kwai Fong district showed a police officer trying to drive his motorbike multiple times into protesters who had gathered on a road.

Police also fired tear gas as they clashed on a university campus with protesters who had built barricades and were throwing projectiles from behind a shield wall of umbrellas.

Monday's shooting is the third time protesters have been shot with live rounds by police. The two previous instances last month came as protesters attacked police officers. The victims, both teenagers, survived their wounds.

With no political solution on the table, officers have been left to battle violent protesters and are now loathed by large chunks of the deeply polarised population.

Immediately after Monday's shooting, crowds of locals gathered to hurl insults at officers who responded with pepper spray and multiple arrests were made.

Police also fired multiple rounds of tear gas at residents and then retreated, ceding the junction once more.

Police have defended their tactics throughout the summer as a proportionate response to protesters who have embraced throwing bricks and petrol bombs as well as vandalising pro-China businesses and beating opponents.

But an independent inquiry into the police has become a core demand of the protest movement, with public anger fuelled by weekly videos of controversial police tactics and aggressive interactions with locals.

In one incident which sparked uproar, a police officer on Friday evening shouting at protesters that he and his colleagues were "opening a bottle of champagne" after the death of the student.

The force said the officer was later reprimanded for his language.

Both Beijing and Hong Kong's unelected leader Carrie Lam have rejected an independent inquiry, saying the city's current police watchdog is up to the task.

The watchdog is due to release a report in early 2020 and in a statement on Monday said the panel's views should not have been published on Twitter by one of its members.

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Hong Kong protest
An independent inquiry into the police force has become one of the key demands of Hong Kong's protest movement. Photo: AFP / Anthony WALLACE