Turkish President Recep Tayyip Erdogan has claimed victory in the referendum on granting him sweeping new powers, saying it was won by a clear majority.
He addressed a rally in Istanbul as the count neared completion. With more than 99% of ballots counted, “Yes” was on 51.35% and “No” on 48.65%.
Erdogan supporters say replacing the parliamentary system with an executive presidency will modernize the country.
The two main opposition parties are challenging the results.
The “Yes” vote, if confirmed, could also see Mr. Erdogan remain in office until 2029.
The president would be given vastly enhanced powers to appoint cabinet ministers, issue decrees, choose senior judges and dissolve parliament.
The new system would scrap the role of prime minister and concentrate power in the hands of the president, placing all state bureaucracy under his control.
Three people were shot dead near a polling station in the south-eastern province of Diyarbakir, reportedly during a dispute over how they were voting.
Supporters are streaming into the governing AK party’s headquarters in Ankara, car horns and campaign songs blaring – they are convinced the “Yes” side has won and that President Erdogan now has a mandate for the biggest political reform in Turkey’s modern history.
Mr. Erdogan said the changes were needed to address Turkey’s security challenges nine months after an attempted coup, and to avoid the fragile coalition governments of the past.
“This public vote is [about] a new governing system in Turkey, a choice about change and transition,” he said after casting his vote in Istanbul.
The new system, he argued, would resemble those in France and the US and would bring calm in a time of turmoil marked by a Kurdish insurgency, Islamist militancy and conflict in neighbouring Syria, which has led to a huge refugee influx.
The Republican People’s Party (CHP) has demanded a recount of 60% of the votes.
Critics of the proposed changes fear the move would make the president’s position too powerful, arguing that it would amount to one-man rule, without the checks and balances of other presidential systems.
They say his ability to retain ties to a political party would end any chance of impartiality. Kemal Kilicdaroglu, leader of the CHP, told a rally in Ankara a “Yes” vote would endanger the country.