Voting begins in Turkey as Erdogan aims to remain in power
The constitutional changes proposed in Sunday’s vote could significantly expand the powers of the country’s top office.
Supporters say a ‘Yes’ vote would streamline and modernise the country, but opponents fear it could lead to greater authoritarianism in the country.
A vote in favour of the radical changes would also see President Recep Tayyip Erdogan remain in office until 2029.
Around 55 million people are eligible to vote across 167,000 polling stations.
Polling stations opened in eastern Turkey at 7am local time (4am BST), with voting in the rest of the country starting at 8am local time (5am BST).
All polling stations have now closed, with counting beginning immediately.
Results are expected to be announced late on Sunday evening.
President Erdogan addressed his supporters in Istanbul on Saturday night, for a final time ahead of voting, calling on citizens to vote in favour of the constitutional changes.
He said: "[The new system] will strengthen the stable and secure environment our country needs to develop.”
This is a live story – refresh for updates.
3pm BST: Polls have now closed in the rest of Turkey. Counting begins immediately.
2pm BST: Polls have now closed in the east and south east of the country, including Diyarbakir. The rest of the country has just one hour left to cast their ballots.
1.45PM BST: Local media reports a third person has now died following an earlier exchange of gunfire outside a polling station in Cermik, Diyarbakir in the south east of the country.
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12.20pm BST: Opinion polls show a slight lead in favour of a 'YES' vote.
11.25am BST: More than one million ballots will be cast today by first-time voters – those who have recently turned 18.
Incredibly, thousands of prisoners will also be able to vote at any of the 463 polling stations set up inside state prisons.
Although the Supreme Election Board has not confirmed an exact number, Turkish national newspaper Milliyet estimates that around 78,890 convicted prisoners will be eligible.
President Erdogan casts his ballot at a polling station in Istanbul
11.10am BST: The Turkish Health Ministry is providing transport and assistance to sick and elderly voters.
10.55am BST: Two people have been killed and at least one other injured in an exchange of gunfire between two groups at a polling station in Cermik, Diyarbakir in the south east of the country. Reports on local media suggest the violence was triggered by opposing political views between two groups of voters.
10.45am BST: Famous faces in Turkey have come out to vote today. In the past hour, singer Tarkan and chef/restauranteur Nusret “Salt Bae” Gökçe have cast their ballots.
10am BST: Mr Erdogan says the changes will address the security challenges faced by Turkey – the referendum vote comes just nine months after a failed coup attempt in the country.
The president claims the new system will resemble those in France and the US, and will bring calm in a time of turmoil marked by a Kurdish insurgency, Islamist militancy and conflict in neighbouring Syria that has led to a huge refugee influx.
President Erdogan addressed supporters in Istanbul on Saturday
9.45am BST: Prime Minister Binali Yildirim votes at a school in Izmir province, near the Aegean coast in western Turkey.
9am BST: President Recep Tayyip Erdogan casts his ballot at a polling station in Istanbul.
8am BST: Kurdish militants have killed a guard in an overnight attack on a vehicle carrying a district official from Yildirim's ruling AK Party.
The attack, in southeast Turkey's Van province, was carried out by Kurdistan Workers Party (PKK) militants in the Van's Muradiye district.
A second AKP guard was wounded, and security services say 17 people have been detained.
5am BST: Polls open across the rest of Turkey.
4am BST: Poll open in eastern Turkey.