The piercing sound of whistles and vuvuzelas resonated through downtown Belgrade on Saturday as the city braced for a large-scale protest against populist President Aleksandar Vucic and his administration.

Massive crowds have been gathering in downtown Belgrade for what is considered the peak of months-long, nearly daily anti-corruption demonstrations, posing the most significant challenge to Vucic’s 13-year stronghold on Serbia’s leadership.

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On Friday evening, tens of thousands enthusiastically welcomed students who had been walking or cycling for days from various parts of Serbia to reach Belgrade for Saturday afternoon’s main protest. From early morning, people began assembling in different parts of the city, preparing to march towards the centre.

Tensions have intensified in the lead-up to the demonstration, with Vucic repeatedly alleging plans for unrest and issuing threats of arrests and severe penalties for any disturbances.

Raising concerns of potential clashes, Vucic’s supporters have set up camp in central Belgrade in front of his headquarters. Among them are former members of a notorious paramilitary unit implicated in the 2003 assassination of Serbia’s first democratic Prime Minister, Zoran Djindjic, along with football hooligans known for inciting violence.

On Saturday, private broadcaster N1 aired footage showing dozens of young men wearing baseball caps entering the pro-Vucic encampment.

Interior Minister Ivica Dacic informed state broadcaster RTS that 13 people had been detained overnight, though no major incidents were reported on Friday. He stated that six opposition activists were arrested on allegations of plotting to instigate a coup and provoke unrest on Saturday.

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Students have spearheaded the nationwide anti-corruption movement, which emerged following the collapse of a concrete canopy at a train station in northern Serbia on 1 November, killing 15 people.

Many in Serbia attribute the tragedy to widespread government corruption, negligence, and disregard for construction safety regulations.

Vucic has accused Western intelligence agencies of orchestrating the near-daily student-led protests as part of an effort to remove him from power.

The students have resonated with citizens frustrated by politicians and disillusioned with state institutions. Previous student-led protests in other Serbian cities have remained peaceful while attracting vast crowds.