ISTANBUL — Turkey's main opposition party is closing in on victory in the main cities of Istanbul and Ankara, in high-stakes local elections.

Istanbul's opposition mayor Ekrem Imamoglu, who won the city in 2019, said that he was "very happy" so far.

A year after Recep Tayyip Erdogan secured a third term as president, he had made it his goal to win back the city where he grew up and became mayor.

But the night belonged to the opposition as it closed in on victory.

With 80% the vote counted in Istanbul, Imamoglu was almost 10 points ahead of his rival from Erdogan's AK Party.

In the capital Ankara, his colleague in the secular opposition CHP, Mansur Yavas, was so far ahead of his rival that he declared victory when less than half the votes were in.

President Erdogan, 70, had led his party's election campaign in Istanbul, vowing a new era in Turkey's biggest city.

The outcome was being as a significant blow for the man who has led Turkey for the past 21 years.

Significantly, the opposition CHP was also leading in many of Turkey's other big cities, including Izmir and Bursa, and the resort of Antalya.

Crowds in Istanbul, a megacity of almost 16 million people, gathered outside one of the main town halls. They waved Turkish flags and banners showing Imamoglu's picture alongside Turkey's founding father Kemal Ataturk.

"I can say that our citizens' trust and faith in us has been rewarded," said Imamoglu.

Both he and Mansur Yavas are seen as potential candidates to run for the presidency in 2028.

"Everything is going to be great," Imamoglu supporters chanted as they danced to drums and clarinets in Sarachane, one of Istanbul's oldest districts.

Istanbul's incumbent mayor had first used the slogan when he won the city from Erdogan's party five years ago. Some of the banners in Sarachane used his current slogan, "Full speed ahead".

"They're only local elections but the opposition's victory in big cities is a significant show of force against the ruling party," Imamoglu supporter Yesim Albayrak, 25, told the BBC.

I am now hoping the country will become a more secular country, respecting human rights, women's rights and children’s rights

Mehmet Bankaci, 27, told the BBC there was a need for change in Turkey: "If Imamoglu or Mansur Yavas had been the CHP candidate in last year's presidential election, they definitely would have won."

Five years ago, Imamoglu overturned years of AK Party rule in Istanbul with the backing of a unified six-party opposition. But that fell apart in the wake of last year's presidential election defeat and the AK Party had high hopes of overturning his 2019 victory.

Ahead of Sunday's election in Istanbul, the vote was seen as too close to call, with the incumbent mayor facing a strong challenge from AK Party candidate Murat Kurum.

But the ruling party has been unable to shake off an economic crisis that has seen inflation rates of 67% and interest rates at 50%.

Erdogan's AK Party has had more success in areas of the south-east devastated by the February 2023 double earthquake. It is leading in the cities of Kahramanmaras and Gaziantep.

About 61 million Turkish voters were eligible to take part in Sunday's election and turnout was estimated at more than 76% across the country's 81 provinces. — BBC