Several thousands of Serbians have staged a protest rally to denounce alleged government violence against political opponents and the media.

The demonstrators — around 5,000 individuals by police estimates — marched through the streets in the capital, Belgrade, on Saturday, demanding policy changes by President Aleksandar Vucic and his ruling Serbian Progressive Party.

The peaceful rally was held to condemn an assault on the leader of the Serbian Left Party, Borko Stefanovic, who was attacked by a group of men wearing black clothing in the southern city of Krusevac on November 23.

The opposition politician suffered minor injuries after being beaten with an iron rod, and the attackers were reported to have been arrested shortly after the incident.

Serbian protesters claimed that the supporters of the 48-year-old president had been involved in the assault, a charge that has been denied by the government.

Opposition groups and activists in Serbia accuse the government of corruption, violence, and stifling press freedoms. They say the Serbian president has maintained an authoritarian rule over the country.

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 holds a majority at the 250-seat parliament.