Clashes broke out in Belgrade after tens of thousands of people protested against Serbia's government.
Riot police were out on the streets as night fell and some in the crowd threw flares, rocks, and bottles.
Police responded with pepper spray as they charged forward and images showed people being detained by what appeared to be plain-clothes officers.
Long lines of cars earlier entered Belgrade despite government attempts to stifle previous demonstrations.
Serbia's rail company cancelled all trains to and from the city on Saturday in an apparent bid to block people from outside the capital.
The protesters in Slavija Square, many with banners and T-shirts inscribed with the "Students win" motto of the youth movement, oppose Aleksandar Vucic's authoritarian rule and want an early election.
They accuse the government of crime and corruption, and demand adherence to the rule of law.
An anti-corruption protest movement gained momentum in Serbia after the deaths of 16 people in a canopy collapse at a train station in November 2024.
The then-prime minister resigned but authorities cracked down hard on further dissent.
Undeterred, protesters were back out in force today with banners declaring "the students are winning" and badges reading "your hands are bloody".
Supporters of President Vucic, who's been in power since 2017, gathered in a nearby park but the daytime protest passed peacefully despite fears of clashes between the two groups.
Parliament speaker Ana Brnabic said the student rally "offered nothing new" and claimed democracy was "flourishing" in Serbia. She cited a police estimate that 34,300 people had attended.
Mr Vucic is in the spotlight for how his right-wing populist government treats the protesters.
There are claims - denied by the government - that a sonic weapon was used on people during a previous rally in Slavija Square in March 2025.
Michael O'Flaherty, the Council of Europe's human rights chief, criticised the Serbian government this week and said he would "monitor the situation closely" on Saturday.
He cited "reports of police protecting unidentified and often masked attackers of journalists and protesters" and said the situation had deteriorated since he visited last year.
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Serbia applied to join the European Union in 2009 and negotiations began a few years after. However, its close links with Russia and concerns over democratic backsliding are proving major hurdles.
Mr Vucic and pro-government media have dismissed critics as foreign agents who wish to destroy the country.
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