Opposition parties aim to challenge the result of the referendum
Turkish President Recep Tayyip Erdoğan has claimed victory in a historic referendum which will grant him sweeping new powers.
State-run Anadolu news agency said the President narrowly won with YES at 51.4% and NO at 48.7%.
The changes will replace Turkey's parliamentary system of government with a presidential one and could see Mr Erdogan remain in office until at least 2029.
The referendum comes six months after a military coup failed to unseat President Recep Tayyip Erdogan on July 15th 2016.
Head of Turkey's Election Board said the voting difference was 1.25 million in favour of yes vote out of 55 million voters.
He also said that they had finally confirmed the result of the Turkish referendum.
BREAKING: The head of Turkey's elections board has confirmed the passage of a referendum expanding presidential powers.— The Associated Press (@AP) April 16, 2017
Opposition parties say they will object to results released by state news agency, saying that there is manipulation.
The head of the main opposition party the Republican People’s Party (CHP) says the referendum has taken place in "unfair circumstances" and that those on the Yes side have gone beyond legal limits.
The referendum has bitterly divided Turkey, and will affect the country's strained relations with the European Union.
Turkish expatriates are said to have played a crucial roll in the referendum with 2.5 million Turks voting in Europe, 95,000 in the US and 45,000 in Australia.
President Erdogan has insisted the changes are needed to amend the current constitution, which was written by generals following a military coup in 1980, to confront security and political challenges in Turkey and avoid fragile coalition governments of the past.
Critics say the move grants sweeping powers to Mr Erdogan following a failed coup last July.
A statement on the High Electoral Board's website hours before polls closed said it would count ballots that had not been stamped by officials as valid unless they could be proved fraudulent.
After casting his vote in a school near his home in Istanbul, Mr Erdogan said "God willing I believe our people will decide to open the path to much more rapid development.
"I believe in my people's democratic common sense." Around 55 million people were eligible to vote in the referendum.
Under the proposals, the office of prime minister would be abolished, allowing the president to draft the budget, declare a state of emergency and issue decrees overseeing ministries without parliamentary approval.