BELGRADE, Serbia (AP) - Thousands of people have marched in Serbia against the autocratic rule of President Aleksandar Vucic and his government.

An opposition alliance called Saturday's protest after assailants recently beat up and seriously injured a leftist party leader and his associates in a southern Serbian city.

The opposition parties have blamed the incident on what they describe as an atmosphere of violence and intimidation imposed by Vucic's populist ruling coalition.

Vucic is a former extreme nationalist who now says he wants Serbia to reform and join the European Union. But critics at home say Vucic has restricted democratic and media freedoms in the Balkan country.

The demonstration in Belgrade was dubbed "Stop to bloody shirts," a reference to the recent beating of Borko Stefanovic, the leader of the Serbia's Left party.

People march during a protest in front of the Serbian Parliament building in Belgrade, Serbia, Saturday, Dec. 8, 2018. Thousands of people are marching in Serbia against the hardline rule of President Aleksandar Vucic and his government. (AP Photo/Darko Vojinovic)

People hold a banner that reads: ''Stop to bloody shirts'' during a protest in Belgrade, Serbia, Saturday, Dec. 8, 2018. Thousands of people marched in Serbia against the autocratic rule of President Aleksandar Vucic and his government. An opposition alliance called the protest on Saturday after assailants recently beat up and seriously injured a leftist party leader and his associates in a southern Serbian city. (AP Photo/Darko Vojinovic)