A Hong Kong anti-government protester has been shot by police in a scene caught on video as demonstrators blocked train lines and roads in a day of spiralling violence fuelled by demands for democratic reforms.
Elsewhere, a man was set on fire following an apparent dispute over national identity in the semi-autonomous Chinese territory, which has been wracked by five months of protests.
The man was in critical condition in a city hospital.
The violence is likely to further inflame passions in Hong Kong after a student who fell during an earlier protest died on Friday and police arrested six pro-democracy lawmakers over the weekend.
Monday's video shows a police officer shooing away a group of protesters at an intersection, 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 area of the second protester, who falls to the ground. The officer appeared to fire again as a third protester in black joined the tussle.
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 that he was undergoing surgery. A spokeswoman for the Hong Kong hospital authority said the person shot was in critical condition but gave no further details.
The incident marked the second time a protester has been shot since the demonstrations began in early June, although police have repeatedly drawn their firearms to ward off attacks. More than 3300 people have been arrested in the protests.
Few details were available about the burning incident in the Ma On Shan neighbourhood. Video posted online shows the victim arguing with a group of young people before someone douses him with a liquid and strikes a lighter.
Police fired tear gas and deployed a water cannon in various parts of the city on Monday and charged onto the campus of Chinese University, where students were protesting.
Video posted online also showed a policeman on a motorcycle riding through a group of protesters in an apparent attempt to disperse them.
Rail service was partly suspended because of fires and obstacles on the tracks and windows were smashed at a branch of the state-owned Bank of China.
Large parts of the downtown business district were closed to traffic as protesters surrounded by onlookers engaged in a standoff with police.
Monday's shooting occurred in a crosswalk at a large intersection strewn with debris that had backed-up traffic in Sai Wan Ho, a neighborhood on the eastern part of Hong Kong Island.
In a news release, the Hong Kong government said police had been responding to vandalism and disruptions to traffic, including protesters throwing heavy objects onto roads from above.
"During police operations, one police officer has discharged his service revolver, one male was shot," the release said, adding that officers also drew their guns in the Shatin and Tung Chung neighborhoods.
"All police officers are required to justify their enforcement actions," the statement said.
The city has been rocked by the death on Friday of a university student who fell from a parking garage when police fired tear gas at protesters.