Hong Kong police have opened fire and hit at least one protester, witnesses and media reports say, as chaos erupted across the city a day after officers fired tear gas to break up demonstrations that are entering their sixth month.

Police fired live rounds at protesters on the eastern side of Hong Kong island, Cable TV and other Hong Kong media reported on Monday. Cable TV said one protester was wounded when police opened fire.

Video footage showed a protester lying in a pool of blood with his eyes wide open. Police also pepper-sprayed and subdued a woman nearby as plastic crates were thrown at officers, the video shared on social media showed.

The footage could not immediately be authenticated.

The Hospital Authority told Reuters a 21-year-old man suspected to have been wounded during the incident in Sai Wan Ho on Hong Kong island was admitted to hospital on Monday and was undergoing an operation.

Cable TV reported that the unidentified protester was in a stable condition.

A Reuters witness said police later fired tear gas in the same area where the protester was shot.

Police said in a statement radical protesters had set up barricades at multiple locations across the city and warned the demonstrators to “stop their illegal acts immediately”.

They did not comment immediately on the apparent shooting.

Anson Yip, a 36-year-old Sai Wan Ho resident, said protesters were throwing rubbish to create a road block when police, possibly from the traffic department, ran to the scene.

“They didn’t fight and the police ran and directly shot. There was three sounds, like ‘pam, pam, pam’,” Yip said.

“They are against the government, that’s why the police just shot them,” he said.

Police have previously shot an 18-year-old protester and a 14-year-old, both of whom survived.

Protesters are angry about what they see as police brutality and meddling by Beijing in the former British colony’s freedoms, guaranteed by the “one country, two systems” formula put in place when the territory returned to Chinese rule in 1997.

China denies interfering and has blamed Western countries for stirring up trouble.

The latest violence comes after a student died in hospital last week following a high fall as protesters were being dispersed by police.

Services on some train and subway lines were disrupted early on Monday, with riot police deployed near stations and shopping malls.

Activists blocked roads and trashed shopping malls across Hong Kong’s New Territories and Kowloon peninsula on Sunday during a 24th straight weekend of anti-government unrest.

The violence spread to the Kowloon district of Mong Kok, one of the world’s most densely populated areas. Police used water cannon and volley after volley of tear gas to try to clear the main artery of Nathan Road.

-AAP