Thousands gathered in Serbia to protest against the assault of an opposition politician and to demand policy changes from the country's president.

Demonstrators chanted as they marched through Belgrade city centre under the slogan "Stop the bloody shirts" on Saturday to condemn the assault on Borko Stefanovic, leader of the small Serbian Left party.

Mr Stefanovic suffered minor injuries after he was attacked and beaten with an iron rod by a group of men dressed in black in the southern city of Krusevac last month.

Serbia’s president Aleksandar Vucic said Mr Stefanovic’s assailants were arrested shortly after the incident.

But opposition figures claimed that his Serbian Progressive Party was involved – something the group's leaders vehemently denied.

“The struggle must be waged with loud chanting against this disgusting, slimy regime,” Branislav Trifunovic, an actor and a protest leader, told the cheering crowd on Saturday.

Opposition activists claimed Mr Vucic was an autocrat and branded his Serbian Progressive Party as corrupt.

“Corruption, violence, stifling of press freedoms, they [the Progressive party] do it all and Vucic is their kingpin,” said 49-year-old mechanic Radovan Peric, from Belgrade.

A woman holds a placard during a protest against violence on 8 December, 2018 in Belgrade. (AFP/Getty Images)

Mr Vucic’s approval ratings have slipped since he won a 2016 presidential vote by a landslide, but he remains the country’s most popular political leader and his ruling coalition has a comfortable majority of 160 deputies in the 250-seat parliament.

Saturday’s rally was called by former Belgrade mayor Dragan Djilas, leader of the Alliance for Serbia - a heterogeneous group of 30 parties - who described the protest as a gathering of citizens against authoritarian rule.

Opposition protests have been relatively rare in Serbia since the popular unrest that ousted former strongman Slobodan Milosevic in 2000.

Mr Vucic, a nationalist firebrand during the violent collapse of the former Yugoslavia in the 1990s, later embraced European values and set Serbia’s membership in the European Union as the country’s strategic goal.

He also maintains close ties with Russia and China.