Turkey's long-standing leader Recep Tayyip Erdogan has won a new five-year term after securing outright victory in the first round of a presidential poll.
Election authority chief Sadi Guven said the president "received the absolute majority of all valid votes".
State media reports put Mr Erdogan on 53% with 99% of votes counted, and his closest rival Muharrem Ince on 31%.
The opposition is yet to officially concede but said it would continue its democratic fight "whatever the result".
It had earlier cast doubt on results being broadcast by state media. Final results will be announced on Friday.
The polls were the most fiercely-fought in many years, and Mr Erdogan is set to assume sweeping powers under a new executive presidency.
He has presided over a strong economy and built up a solid support base by investing in healthcare, education and infrastructure.
But the 64-year-old has also polarised opinion, cracking down on opponents and putting some 160,000 in jail.
Mr Erdogan gave a triumphant victory speech from the balcony of his party's headquarters in the capital Ankara at 03:00 (00:00 GMT), declaring: "The winner of this election is each and every individual among my 81 million citizens."
Supporters of Erdogan and the AK Party took to Istanbul's streets to celebrate
There are reports that Republican People's Party (CHP) presidential candidate Mr Ince has admitted defeat in a message to a journalist, though this has not been confirmed.
Earlier on Sunday he accused state-run news agency Anadolu of "manipulation" over its reporting of vote-share figures.
Mr Ince tweeted that he would make a statement at 12:00 (09:00 GMT) on Monday.
President #Erdogan heads to Ankara to give a balcony speech. Main challenger #MuharremÄ°nce reportedly just conceded defeat via a WhatsApp message to a reporter, saying “It wasn”™t a fair race but I accept that Mr Erdogan has won,” adding that he”™d make a statement tomorrow
— Selin Girit (@selingirit) June 24, 2018
There were another four candidates on the presidential ballot, none of whom appears to have won more than 8.4% of the vote.
President Erdogan will assume major new powers under Turkey's new constitution. The changes were endorsed in a tight referendum last year by 51% of voters, and are due to come into force after the election.
The job of prime minister will also be scrapped.
Some critics argue the enhanced role will place too much power in one person's hands, and that Turkey's new system lacks the checks and balances of other executive presidencies like France or the US.
Mr Erdogan maintains his increased authority will empower him to address Turkey's economic woes and defeat Kurdish rebels in the country's south-east.
In his victory speech, he said Turkey would act more firmly against terrorist groups, and would continue to "liberate Syrian lands" so refugees can return to their homes there.