PRO-European Union candidate Nicusor Dan won Sunday’s closely watched presidential run-off in Romania against a far-right candidate who modelled his campaign after United States President Donald Trump.

The victory marked a major turnaround in a tense election that many viewed as a geopolitical choice for the former Eastern Bloc country between East or West.

The race pitted George Simion, the leader of the far-right Alliance for the Unity of Romanians (AUR), against Mr Dan, the incumbent mayor of Bucharest.

It was held months after the cancellation of the previous election plunged Romania into its worst political crisis in decades.

Mr Dan was ahead with 53.9 per cent, while Mr Simion trailed at 46.1 per cent, according to official data.

In the first-round vote on May 4, Mr Simion won almost twice as many votes as Mr Dan, and many local surveys predicted he would secure the presidency.

But Mr Dan picked up almost 900,000 more votes to solidly defeat his opponent in the final round.

On Sunday evening, thousands rallied outside Mr Dan’s headquarters near Bucharest City Hall to await the final results, chanting “Nicusor!"”

Once it was clear he had secured a victory, Mr Dan said: “What you have done as a society in these past weeks has been extraordinary.

“Our full respect for those who had a different choice today, and for those who made a different choice in the first round. We have a Romania to build together, regardless of political choices.”

Final electoral data showed a 64 per cent voter turnout — a sharp increase from the first round on May 4 where 53 per cent of eligible voters cast a ballot.

Romania’s political landscape was upended last year when a top court voided the previous election in which far-right outsider Calin Georgescu topped first-round polls, following allegations of electoral violations and Russian interference, which Moscow denied.