Latest: Erdogan declares victory in Turkey's constitutional referendum despite opposition objections
Turkey's president Recep Tayyip Erdogan declared victory in Sunday's referendum that will grant sweeping powers to the presidency, hailing the result as a "historic decision".
Speaking to reporters in Istanbul, Mr Erdogan said unofficial results showed the "yes" side had won by a margin of 1.3 million votes.
The president struck a conciliatory tone, thanking all voters regardless of how they cast their ballots and describing the referendum as a "historic decision".
"April 16 is the victory of all who said yes or no, of the whole 80 million, of the whole of Turkey of 780,000-square kilometres," Mr Erdogan said.
Turkey's prime minister has declared a victory based on unofficial results for backers of a referendum to greatly expand the powers of the country's president.
Opposition figures questioned the result, however, and indicated they would challenge some of the counts.
Results carried by the state-run Anadolu news agency showed the "yes" vote had about 51.3% compared to 48.7% for the "no" vote with nearly 99% of the vote counted.
Addressing thousands of flag-waving supporters on tonight, prime minister Binali Yildirim said the "unofficial' final result is 'yes'" for the constitutional referendum.
Mr Yildirim spoke on the balcony of his governing AK Party headquarters in Ankara, addressing a crowd of about 3,000 people who waved flags and chanted the name of the country's president, Recep Tayyip Erdogan.
Earlier, the leader of Turkey's main nationalist party also claimed victory.
Nationalist Action Party head Devlet Bahceli said in a statement that Turkish voters chose of their free will to move the country from a parliamentary to a presidential system of government.
Mr Bahceli called the outcome "a very important success; a win that makes neglect and denial impossible".
He said Turkey rejected international "pressure, blackmail, imposition, force and threats by the whole world to put the 'no' choice forward".
The party, the fourth largest in parliament, backed Mr Erdogan and the governing Justice and Development Party in their push to change Turkey's parliamentary system into a presidential one.
The main opposition party said it will challenge 37% of the ballot boxes counted.
Republic People's Party, or CHP, deputy chairman Erdal Aksunger predicted the figure could even increase to 60%.
Mr Aksunger said: "Since this morning, we have determined some 2.5 million problematic votes."
The country's pro-Kurdish opposition party, which also opposed the constitutional changes, says it plans to object to two-thirds of the ballots.
The Peoples' Democratic Party said on its Twitter account: "Our data indicates a manipulation in the range of three to 4%."
