By order of the Supreme Election Council (YSK), all campaigning and opinion broadcasts ahead of Sunday's presidential and parliamentary elections ended as of 6 p.m. local time (1500 GMT) on Saturday.
Voting started at 0500GMT (8 am local time) and will continue through to 1400 GMT (5 pm local time).
Turkey has been under emergency rule - which restricts some personal freedoms and allows the government to bypass parliament with emergency decrees - for almost two years following an abortive military coup in July 2016. If a candidate wins just over 50 percent of the vote, he will win the presidency, but if not, there will be a runoff on July 8.
Other presidential candidates include Selahattin Demirtas, leader of the pro-Kurdish Peoples Democratic Party (HDP), who is now in jail on terrorism-related charges that he denies.
Supporters of Turkish President Tayyip Erdogan attend an election rally in Istanbul, Turkey, June 23, 2018.
It's the first time they'll be voting for president and parliament at the same time - a change approved previous year by a referendum that switched Turkey's governance system to an executive presidency.
More than 59 million Turkish citizens, including some 3 million living overseas, are eligible to vote on Sunday.
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The US now imposes a 2.5% tariff on imported passenger cars from the European Union and a 25% tariff on imported pick-up trucks. Beijing has vowed to immediately retaliate with its own tariffs on US soybeans and other farm products in a direct shot at Mr.
"Let this immorality be an example to the world", said Mr Ince, who said he had held 107 rallies around Turkey in the 51 days since his candidacy was announced.
Voting already closed last week for Turkish citizens resident overseas, with just under 1.5 million out of just over 3 million registered voters casting their ballot, a turnout of just under 49 percent. She broke away from Turkey's main nationalist party over its support for Erdogan and formed the center-right, nationalist Good Party.
"I hope these elections are beneficial and truly reflect the free will of the voters", Aksener told reporters in Istanbul.
The constitutional overhaul would mean that Erdogan could stay in power for another two terms until 2029.
In a final appeal for votes in a video clip from his high security prison, Demirtas said: "If the HDP fails to get into parliament, all Turkey will lose". A party must receive 10 percent of the votes for any of its candidates to win a seat at the legislature.
Meanwhile, former physics teacher Ince built up a national following with lacerating attacks on Erdogan's rule, bringing up near-taboos like the AKP's past cooperation with the group of Fethullah Gulen blamed for the 2016 failed coup. "Backing the HDP means supporting democracy". According to the latest United Nations figures, some 160,000 people have been detained and almost as many more sacked in the crackdown.