BELGRADE, Serbia (AP) — Serbian opposition supporters were back in the streets on Tuesday, accusing President Aleksandar Vucic’s populist government of orchestrating fraud in last month’s parliamentary and local elections.

The protesters want the Dec. 17 vote to be annulled and held again in free and fair conditions. Similar demonstrations were held for days after the elections.

“The entire planet knows that the thief has been caught stealing,” opposition politician Marinika Tepic told the few thousand protesters. “There are no free and fair elections here. If we give up this fight, there will be no more elections.”

The ruling Serbian Progressive Party was declared the winner, but the main opposition alliance, Serbia Against Violence, claims the election was stolen, particularly in the vote for Belgrade city authorities.

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Both Serbian election authorities and the courts have rejected the complaints lodged by the opposition group over the election.

International observers have said that the election was held in unjust conditions, noting serious irregularities that included ballot box stuffing and vote-buying.

Some local election monitors alleged that voters from across Serbia and neighboring countries were bused in to cast ballots in Belgrade. Local election monitors and opposition supporters alleged that populist supporters were registered at bogus addresses there.

Vucic and his party have called the reports “fabricated.”

In December, tensions soared when police fired pepper spray at protesters who tried to enter Belgrade City Hall and arrested dozens.

The crowd on Tuesday also lit candles at a Belgrade church to mark the killing on Jan. 16, 2018 of a moderate ethnic Serb politician from Kosovo, Oliver Ivanovic.

Kosovo is a former Serbian province whose 2008 declaration of independence is unrecognized by Belgrade. The dispute remains a source of tension in the volatile Balkans.

Serbia is seeking European Union membership but has refused to impose sanctions on traditional ally Russia, partly because Moscow supports Belgrade’s claim to Kosovo.