Election monitors in Serbia reported more than 120 irregularities at polling stations by 11am on Sunday, including breaches of ballot secrecy and problems with voter lists, as the country held a parliamentary election that could challenge the ruling party's 14-year grip on power.
The Centre for Research, Transparency and Accountability (CRTA) said the incidents were recorded across a sample of 750 polling stations. They included voters photographing ballots, voting outside designated booths and group voting.
CRTA also reported cases of voters missing from electoral rolls, incorrect signatures in voting records and suspected irregularities involving voter registrations at certain addresses.
The reports come amid longstanding concerns over an uneven electoral playing field. Vucic's SNS dominates much of the media landscape and has been accused by critics of using state resources and patronage networks to maintain its position.
The investigative outlet BIRN has reported accounts of public-sector employees being pressured to support the SNS, including allegations that workers were asked to provide proof of their voting slips.
The student-backed opposition list, Students Are Winning, also reported suspected irregularities in the southern city of Nis, including alleged duplicate voter lists found at several cafes. Opposition activists and other groups raised suspicions of organised voting and possible vote-buying in separate incidents
In Novi Sad, a dispute erupted after activists alleged that people had been found with a duplicate voter list. In the village of Pavlovci, two journalists were reportedly attacked while trying to film events, according to local media reports.
The Basic Public Prosecutor's Office said a criminal complaint had been filed against two people in Pancevo over suspected violations of ballot secrecy, with one also accused of coercion.
The incidents add to concerns about electoral fairness as the student movement seeks to translate nearly two years of anti-government protests into votes against the SNS.
The Organisation for Security and Cooperation in Europe (OSCE) has deployed observers across Serbia. Its Office for Democratic Institutions and Human Rights is due to publish preliminary findings on Monday.