An unofficial vote count indicates prime minister Recep Tayyip Erdogan is set to win Turkey's first ever presidential election in the first round, according to the state-run Anadolu news agency.
Anadolu said that with nearly 52 per cent of ballot boxes opened, Mr Erdogan had the support of 55.68 per cent.
His main rival, Ekmeleddin Ihsanoglu, had 35.79 per cent and the third candidate, Selahattin Demirtas, had 8.41 per cent.
Turkey’s electoral commission is not expected to announce any official results until tomorrow.
An absolute majority is needed to win and avoid a run-off vote on August 24th.
Late today, Mr Erdogan emerged from his house in Istanbul and was greeted by a crowd of supporters cheering and chanting "Turkey is proud of you".
Now in his third term as prime minister at the head of the Islam-rooted Justice and Development Party, or AKP, Erdogan has been a polarising figure.
He is fervently supported by many as a man of the people who has led Turkey through a period of economic prosperity. But his critics view him as an increasingly autocratic leader bent on concentrating power and imposing his religious and conservative views on a country founded on strong secular traditions.
Fadi Hakura, an associate fellow at the Chatham House think tank in London, said an Erdogan win would likely mean a continuation of his confrontational mode of leadership.
“I don’t think that this really will change Turkey that much. Essentially if you look at prime minister Erdogan’s style of governance, at least in the last four or five years, it’s been increasingly singular, dominant, combative, confrontational and ideological,” Mr Hakura said before the elections.
“So I don’t think that (his) assumption of the presidency will change the ... nature and character of Turkey’s style of governance.”
Previously a largely ceremonial role, Mr Erdogan has vowed to transform the presidency into a powerful position. He has said he will activate the post’s rarely used dormant powers - a legacy of a 1980 coup - including the ability to call parliament and summon and preside over cabinet meetings.
Party rules barred Mr Erdogan from serving another term as prime minister. Turkish presidents used to be elected by parliament, but Mr Erdogan’s government pushed through a constitutional amendment in 2007, changing the procedure to a popular vote.
Mr Ihsanoglu, the 70-year-old former head of the Organisation of Islamic Cooperation and a political newcomer, seemed not to have won over the electoral base of the several parties backing him, and there had been few doubts of an Erdogan win.
He is backed by several opposition parties, including the two main ones: a pro-secular party and a nationalist one, and ran on a platform stressing unity.
Speaking after voting in Istanbul, Mr Ihsanoglu said some voting irregularities had been reported, such as voters photographing their stamped ballots with their mobile phones. He said an official complaint would be filed.
“The eyes of the whole world are upon us,” he said. “(Turkey) has been striving to become a first-class democracy ... and hopefully Turkey will achieve this today.”
Press Association