A man has been set on fire following an apparent dispute over national identity in Hong Kong, where police also shot a protester on a day of escalating violence.

The man set on fire was in a critical condition in hospital. Video posted online shows him arguing with a group of young people, before someone douses him with a liquid and flicks open a lighter.

The police shooting was also captured on video Monday, as demonstrators blocked railway lines and roads during the morning rush hour to push their demands for democratic reforms.

The Hong Kong hospital authority said the person shot was in a critical condition.

The violence is likely to further inflame passions after a student died Friday from injuries suffered in an earlier fall and police arrested six pro-democracy lawmakers over the weekend.

The video of the police shooting shows an officer moving away a group of protesters at a road junction, then drawing his gun on a masked protester in a white hooded sweatshirt who approaches him.

As the two struggle, another protester in black approaches, and the officer points his gun at the second one.

He then fires at the stomach of the second protester, who falls to the ground.

The officer appeared to fire again as a third protester in black joined the tussle.

Hong Kong Protests
Protesters with umbrellas and bottles of water to douse tear gas canisters form up during a confrontation with police (Vincent Yu/AP)

The protester in white manages to flee, bounding up a nearby stairway, and the officer and a colleague pin the two in black to the ground.

Police said that only one protester was hit and he was undergoing surgery.

A spokeswoman for the Hong Kong hospital authority said the person shot was in critical condition.

Hong Kong is in the sixth month of protests that began over a proposed extradition law and have expanded to include demands for greater democracy and police accountability.

Activists say Hong Kong’s autonomy and Western-style civil liberties, promised when the former British colony was returned to China in 1997, are eroding.