Angry protesters have set fire to the offices of Serbia's governing populist party in a western town and clashed with police in the capital Belgrade in another evening of violent protests shaking the Balkan country.

Police fired tear gas at anti-government protesters in downtown Belgrade as they clashed for the third day on Friday in the Serbian capital and other cities amid reports of police brutality and excessive use of force during the unrest.

Serbia's police used teargas and crowd control vehicles on Friday evening in Belgrade to disperse anti-government protesters who threw firecrackers and flares at police officers in what is seen as a major escalation of the nine-month-long protests.