"According to the result as of now, my competitor Ekrem Imamoglu is leading the race".
With 96.6 percent of votes counted, Anadolu said that Imamoglu was ahead with 53.71 percent, while Yildirim, a former prime minister and close ally of Erdogan, on 45.29 percent. Turkey's lira currency tumbled after the decision to annul the March vote and is down almost 10% this year in part on election jitters.
Imamoglu had won the original mayoral election on March 31 by a narrow margin, which prompted the Islamist-rooted AKP to demand a re-run, citing what it said were voting irregularities. He spent 18 days in office before Turkey's electoral board annulled the results after weeks of partial recounts.
The voided vote in Istanbul had raised concerns domestically and overseas about the state of Turkish democracy and whether Erdogan's party, which has been in control of the Turkish government since 2002, would accept any electoral loss.
"You protected the dignity of Turkey's democracy in front of the whole world", the CHP candidate said. "Mayor again!" Others hung out of cars, blaring horns and waving red-and-white Turkish flags.
Erdogan was Istanbul's mayor in the 1990s before he embarked on a national political career, dominating Turkish politics first as prime minister, then as president.
But he has downplayed the importance of the re-run, saying last week that the choice of mayor was "only a change in the shop window" since the AKP controls nearly two-thirds of the city's districts. Imamoglu will have to work with those officeholders to govern Istanbul.
AKP also lost control of the capital city of Ankara in Turkey's March local elections, which were held as the country faced an economic downturn, battled high inflation and two credit rating downgrades in the past year. "Everything is imported and we can't afford it".
Analysts say the result would increase pressure on Erdogan's government, which is grappling with a shaky economy and multiple worldwide crises.
Opposition candidate Ekrem Imamoglu sought to repeat his win from 12 weeks earlier to become the city's first mayor in 25 years who is not from President Recep Tayyip Erdogan's party or its Islamist-rooted predecessor.
Hintz said the mayor-elect withstood a divisive campaign by the government and prevailed with a positive message. "We believed in him and he believed in us", said 29-year-old Imamoglu supporter Eda Alday, as cars honked and fans waved Turkish flags in the street.