Turkey referendum

In a phone call, the US president also thanked Mr Erdogan for supporting America's missile strike on a Syrian government airbase on 7 April.

In the poll, 51.4% of Turkish voters backed the changes.

Mr Erdogan rejected criticism from international monitors who said he had been favoured by an "unequal campaign".

"Know your place," he told the observers.

The narrow victory was ruled valid by Turkey's electoral body, despite claims of irregularities by the opposition.

Sadi Guven was speaking after the main opposition Republican People's Party (CHP) cited irregularities, including the use of unstamped ballot papers.

President Recep Tayyip Erdogan's push for an executive presidency succeeded with just over 51% voting for it.

The win was met with both celebrations and protests across Turkey.

Deputy Prime Minister Nurettin Canikli said legal changes to introduce the new system could be completed within a year.

New presidential and parliamentary elections are due on 3 November 2019.

The Turkish Election Commission has yet to release its official results, and the opposition promised to contest at least a third of the votes cast. But according to the state-run Anadolu Agency, with 99.8% of the ballots counted, Erdogan appeared poised to win with 51.4% of voters casting ballots in his favor.

A total of 47.5 million votes were cast, Anadolu said.

Binali Yildirim was speaking as the count neared completion. With about 99% of ballots counted, "Yes" was on about 51.3% and "No" on about 48.7%.

Erdogan supporters say replacing the parliamentary system with an executive presidency would modernise the country.

The two main opposition parties are challenging the results.

A "Yes" vote could also see Mr Erdogan remain in office until 2029.

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.

President Recep Tayyip Erdogan is seeking to replace the parliamentary system with an executive presidency.

Approval could see him stay in office until 2029.

Supporters say a "yes" vote would streamline and modernise the country; opponents fear the move would lead to increasingly authoritarian rule.

If the referendum vote falls in Mr Erdogan's favour, it would give him vastly enhanced powers to appoint cabinet ministers, issue decrees, choose senior judges and dissolve parliament.