A policeman has shot at least one person during another day of violence and chaos in Hong Kong.

Footage shown live on Facebook showed the officer drawing his gun before grappling with a man at a roadblock.

Visit the BBC to see the video;  https://www.bbc.com/news/av/embed/p07tlb79/50370715

Another man, wearing a face mask, then approaches and the officer shoots him, hitting him in the torso.

As the grapple continues, the officer fires another two rounds - although it's not clear from the footage whether the bullets hit anyone.

There have been a number of other flashpoints, with police firing tear gas and rubber bullets in others parts of Hong Kong.

What happened at the shooting?

The shootings took place as protesters tried to block a junction at Sai Wan Ho on the north-east of the island.

Police confirmed that one officer "discharged his service revolver" and that "one male was shot".

After being shot, footage showed the protester lying with his eyes wide open and with blood around him.

He is undergoing surgery and is in a critical condition, a Hospital Authority spokesman told the BBC. The spokesman said he was not aware of a second person being injured.

Authorities said that at two other places, officers also drew their firearms from their holsters.

However, police denied "totally false and malicious" reports that it ordered officers to "recklessly use their firearms" in Monday's operations.

It's the third time police have shot someone with live rounds since the Hong Kong protests began in June.

The first incident was during protests on 1 October when China was celebrating 70 years of communist rule. The second case was a teenage boy shot in the leg on 4 October.

What else has happened on Monday?

While most protests have taken place at weekends, protesters called for a general strike - that is, all workers not to work - on Monday.

In addition to the shooting, other clashes included:

• At the Chinese University, police fired rubber bullets in response to protesters throwing bricks
• At Hong Kong Polytechnic, police fired tear gas at a demonstration
• Protesters used barricades to block roads in various places, leading to long traffic jams. MTR railway stations were also targeted
• Police say protesters dropped "large and heavy objects" on roads, endangering drivers
• In one video circulating online, a police motorcycle seems intentionally to ram into protesters.

Police described the activists as "radical protesters," conducting "extensive illegal acts" and urged them to stop any actions that threaten safety and obstruct the police.

Several universities have cancelled their classes for the day.

The latest violence comes after a student died in hospital last Friday after falling from a ledge in a car park, reportedly trying to flee from police tear gas.

Why are there protests in Hong Kong?

Hong Kong is part of China but as a former British colony it has some autonomy and people have more rights.

The protests started in June against plans to allow extradition to the mainland - which many feared would undermine the city's freedoms.

The bill was withdrawn in September but demonstrations continued and now call for full democracy and an inquiry into police behaviour.

Clashes between police and activists have become increasingly violent and in October the city banned all face masks.