Turkish President Recep Tayyip Erdogan on Sunday was leading a tightly contested presidential election with most of the ballots counted, as he seeks a new mandate in the face of a revitalized opposition and weakening economy.
The new system, which narrowly passed in a constitutional referendum in April 2017, will abolish the prime minister's post. Critics say it will further erode democracy in the North Atlantic Treaty Organisation member state and entrench one-man rule.
Polls across the country of 81 million people officially closed at 5 pm (1400 GMT).
If Erdogan wins both the presidency and control of Parliament, observers worry that Turkey could continue a slide from authoritarianism to outright dictatorship. Turkey in turn has pressed Germany repeatedly to hand over people it believes were involved in the coup.
"Turkey is staging a democratic revolution", he told reporters in the polling station.
As of 15:50 GMT, Erdogan is leading in the polls with almost 60 percent of the vote after 20 percent of the ballot boxes were opened.
Erdogan's main rival, Muharrem Ince of the secularist Republican People's Party (CHP), has promised to reverse Turkey's possible swing towards one-man rule under Erdogan.
The rally, held in Istanbul, was in support of Muharrem Ince, the main competitor to President Erdogan. Erdogan has pledged to lift the state of emergency after the elections.
Erdogan's supporters said only he could ensure political and economic stability in Turkey.
Erdogan said there had been no serious voting violations. They argue election law changes and fraud allegations in the 2017 referendum raise fears about the vote's fairness.
The state-run Turkish news agency Anadolu reported Sunday that around 10 Europeans faced legal action including three French citizens, three Germans and four Italians allegedly for acting as election observers without accreditation in the mainly Kurdish southeast. It was not clear whether they were in custody.
Turkey's official Anadolu news agency said challenger Muharrem Ince was in second place, with almost 29% of the vote. Hence it is my duty to warn all civil servants again: "Please everybody do their duty", he said.
The president had for the last two years ruled under a state of emergency imposed in the wake of the 2016 failed coup, with tens of thousands arrested in an unprecedented crackdown, which cranked up tensions with the West.
Mr. Erdogan blamed the coup on his former ally, USA -based Muslim cleric Fethullah Gulen, and has waged a sweeping crackdown on his followers in Turkey, detaining some 160,000 people, according to the United Nations. All we want is a fair competition. "Rights are violated, democracy is in bad shape", said health sector worker Sema, 50, after voting in Istanbul. In the parliamentary election, his AK Party is also in first place with over 47 percent. If it does so, it will be harder for the AKP to get a majority.