Riot police in Serbia have fired tear gas and pepper spray at opposition supporters demanding the annulment of elections marred by claims of widespread fraud, writes Al JAzeera.

Hundreds of protesters attempted to storm Belgrade City Hall on Sunday evening during demonstrations against the results of parliamentary and local elections on December 17, which international observers say were marred by vote buying, ballot stuffing and the improper influence of President Aleksandar Vucic.

Opposition supporters, some chanting, “Vucic thief” and “Vucic is Putin”, used flagpoles and rocks to break windows as they tried to break into the capital’s administrative building but were repelled by riot police.

Vucic’s ruling Serbian Progressive Party (SNS) were returned to power with a parliamentary majority after winning nearly 47% of the votes, according to preliminary results announced by electoral authorities.

The centre-left opposition alliance Serbia Against Violence [SAV] received 23.56% of the vote, followed by the Socialist Party of Serbia with 6.56%, according to electoral authorities. SAV has claimed it was the rightful winner, especially in Belgrade, where there were reports of non-residents being recruited to vote. In a letter earlier this week, SAV told EU institutions, officials and member nations that it would not recognise the outcome and called on the bloc to do the same as well as to initiate an investigation.

Vucic has rejected opposition calls to rerun the vote, blasting claims of irregularities as blatant “lies”. In an address aired by pro-government Pink TV on Sunday, Vucic said the protests were “not a revolution” and those seeking to destabilize the state would not succeed.