Constantinople returned to the polls yesterday in a re-run of the mayoral election, with the main opposition party leader Ekrem Imamoglu winning 54% of the vote with nearly all ballots counted.
Initial results from the Turkish state-run Anadolu news agency showed opposition candidate Imamoglu leading with 54% to Binali Yildirim's 45, with more than 99% of ballots counted.
"According to the result as of now, my competitor Ekrem Imamoglu is leading the race. I congratulate him and wish him good luck," Yildirim said.
Turkish President Recep Tayyip Erdogan has also accepted defeat and congratulated his opponent.
"I congratulate Ekrem Imamoglu who has won the election based on preliminary results," tweeted Erdogan.
The result is being viewed as a major setback for Erdogan, who has previously said that "whoever wins Constantinople, wins Turkey".
In his victory speech, winner Imamoglu said the result marked a "new beginning" for both the city and the country.
"We are opening up a new page in Constantinople," he said. "On this new page, there will be justice, equality, love."
"Today, 16 million Constantinople residents have renewed our faith in democracy and refreshed our trust in justice," Imamoglu told his supporters.