Turkeyâ€™s Recep Tayyip Erdogan is ahead in the presidential election with 52% of votes counted, state media report.
Mr Erdogan has 56%, and his closest rival, Muharrem Ince, is on 29%.
If Mr Erdogan wins more than 50% of the overall vote, he will be declared the winner and avoid the need for a second round of voting.
As well as the presidency, voters are also choosing members of parliament. Mr Erdoganâ€™s party is ahead in that poll.
With 38% of the votes for parliament counted, the presidentâ€™s AK Party leads with 47% of the votes, the state news agency Anadolu reports. The main opposition CHP is on 19%.
Voter turnout is almost 87%, the state broadcaster says.
Initial results were thought likely to favour the AK Party, so Mr Erdoganâ€™s lead is expected to decrease as more votes are counted.
His opponent tweeted that the state news agency was being manipulative by releasing results from pro-Erdogan areas first.
Turkey remains under a state of emergency imposed in the aftermath of a failed coup in July 2016.
These elections were originally scheduled for November 2019 but were brought forward by Mr Erdogan.
He is seeking a second term as president, and would govern under a new constitution which grants the president new powers.
Mr Erdogan was prime minister for 11 years before becoming president in 2014.
Media caption does it matter whoâ€™s in charge of Turkey?
Mr Ince has promised to push back what he characterised as a slide into authoritarian rule under Mr Erdogan, should he win.
But his opponent accused the former physics teacher of not having the skills to lead.
Muharrem Ince is known for his fiery campaigning
Around 60 million Turks were eligible to take part in Sundayâ€™s dual polls.
As well as Mr Erdogan and Mr Ince, there are four candidates on the ballot.
One has to hit the 50% threshold in an outright win, or the top two will face off in a second-round vote on 8 July.