Eight police officers were injured and 38 people were detained during and after an opposition protest over election results, Serbian police said Monday.
Thousands of people gathered in central Belgrade on Sunday to demand the annulment of parliamentary and local elections held a week ago, which international observers deemed unfair.
The protesters broke windows and glass at the main entrance of the town hall, before the police used pepper spray to disperse them around 10:00 p.m. (9:00 p.m. GMT).
Ivica Ivkovic, head of police administration, said two of the eight wounded police officers suffered serious injuries.
"We will continue working to maintain peace and order and we hope that there will be more arrests in relation to last night's protests," Ivkovic declared at a press conference.
Opposition parties accused police of using excessive force, and some social media showed images of police beating men in the streets near city hall.
The outgoing Prime Minister, Ana Brnabic, thanked the Russian secret services for providing information on the activities planned by the opposition. "This (my statement) is not going to be popular in the West," Brnabic of the ruling Serbian Progressive Party (SNS) said in a television program.
A European Union hopeful, Serbia has resisted pressure from Western countries to introduce sanctions against Russia.
Moscow has been one of Serbia's closest allies for decades, especially after 1999, when Russia opposed NATO airstrikes against the former Yugoslavia, made up of Serbia and Montenegro.
Last Monday, an international observation mission noted that the SNS had gained an unfair advantage thanks to media bias, undue influence from President Aleksandar Vucic and voting irregularities such as vote buying.
The opposition, led by the centre-left alliance Serbia Against Violence, said protests would continue on Monday, with students planning to block traffic.
The ruling populist Serbian Progressive Party (SNS) won 46.72% of the vote in last weekend's snap parliamentary elections, according to preliminary results from the state electoral commission.
Serbia Against Violence came in second, with 23.56% of the votes, and the Socialist Party of Serbia in third, with 6.56%.
