Police and protesters exchanged tear gas and petrol bombs in Hong Kong on Sunday amid anger over an attack on a leading activist by men allegedly linked to triad gangsters.

Clashes broke out as tens of thousands took to the streets for an unsanctioned anti-government march, many also defying a face mask ban introduced in a bid to curb the protests.

Tensions ran high after Jimmy Sham, the leader the Civil Human Rights Front which called the march, was attacked earlier in the week by a group of men wielding metal poles and hammers. Witnesses said that those responsible for the assault were associated with pro-Beijing triads that have been blamed for previous violence against protesters.

On Saturday afternoon, a 19-year-old man was also hospitalised after being stabbed in the abdomen while handing out pro-democracy flyers in Tai Po, a district in northern Hong Kong.

Politically motivated attacks and vandalism have been on the rise as the situation continues to escalate in what is now the twentieth consecutive week of protests.

Protesters are now vandalising and destroying shops, banks, and businesses associated with mainland China.

As moderate, peaceful marchers branched off from the more radical, black-clad frontline protesters near Tsim Sha Tsui police station, violence flared.