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, BBC reported.
He was speaking in Istanbul as the count neared completion.
Turkey was on course to switch from a parliamentary to presidential system, with "Yes" campaign leading on 51.3 per cent after 99 per cent of ballots had been counted, the state-run Anadolu Agency reported.
As of 9:35 p.m. local time (1835 GMT), unofficial results showed "Yes" with 51.34 per cent while "No" had 48.66 per cent votes.
The data showed that Turkey's three biggest cities Istanbul, Ankara and Izmir, as well as the predominantly Kurdish southeast voted "No" for the constitutional change that will hand Erdogan sweeping powers.
The President called Prime Minister and ruling Justice and Development (AK) Party leader Binali Yildirim, Nationalist Movement Party (MHP) leader Devlet Bahceli, and Grand Unity Party (BBP) Mustafa Destici, the three leaders who supported the "Yes" campaign, to congratulate them over the referendum victory.
The opposition Nationalist Movement Party (MHP) leader described Sunday's referendum result as a significant success.
"The Turkish people have gone to the polls with a great dignity and decided on shifting to the presidential system of their own free will.
"This is a very significant achievement and cannot be ignored or rejected," Anadolu quoted Devlet Bahceli as saying in a statement.
Bahceli said everybody "should respect and approve" the result in which Turkish citizens voted "Yes" to moving to an executive presidency.
"The great Turkish nation, the sole owner of sovereignty, has given the final word about the future of its country, clinging to its independence and future. Everybody should respect and approve it," he added.
Bahceli congratulated the Turkish people and Turkey's political parties on the "Yes" result and said: "A new era in our state and political life has started as the national will pointed to Yes."
More than 55 million people in the country were registered to vote and more than 1.3 million Turkish voters cast their ballots abroad.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)