Turkey's top election body ordered a re-run of the Istanbul mayoral election on Monday after President Recep Tayyip Erdogan's party complained about its shock defeat in the vote, the state news agency reported.
The new election will take place on June 23, according to the state-run TRT broadcaster.
The ruling Justice and Development Party (AKP) narrowly lost Turkey's biggest city in March 31 local elections, ending the party and its predecessors' 25-year control of the metropolis.
The AKP claims there were "irregularities and corruption" in the vote that required a re-run of the mayoral election, which was won by Ekrem Imamoglu, of the main opposition Republican People's Party (CHP) by just 15,000 votes.
Imamoglu called it a "treacherous decision" and vowed to fight on.
"They are trying to take back the election we won. Maybe you are upset but never lose hope," he told thousands of supporters on the outskirts of Istanbul following the ruling.
Imamoglu received his official mandate after two weeks of recounts, sending shockwaves through the ruling party since Erdogan, former mayor of the city, once said winning Istanbul was like winning the whole of Turkey.
Onursal Adiguzel, deputy chairman of the CHP party, called Monday’s ruling an act of a dictatorship.
'This is plain dictatorship'
“It is illegal to win against the AK Party,” he said in a post on Twitter. “This system that overrules the will of the people and disregards the law is neither democratic, nor legitimate. This is plain dictatorship."
Imamoglu said he would travel to Ankara on Tuesday to meet with party leaders.
"I dont even know what to say. The lawlessness is so obvious," a female supporter told AFP ahead of his speech in Istanbul.
"If there is no rule of law... they will trigger a civil war," she added.
The defeated mayoral candidate, former prime minister Binali Yildirim, said he hoped the re-run would "be beneficial for our city".
Erdogan had presented the local elections as a matter of national survival. He campaigned heavily even though he was not running himself.
The AKP still won the most seats nationwide, but anger over the deteriorating economy led it to lose mayorships in both Istanbul and the capital Ankara.
The party did not request a re-run of the election for the Istanbul local assembly, in which it won a majority of seats.
(FRANCE 24 with AFP, REUTERS)
