President Trump congratulates Erdogan on referendum victory
US President Donald Trump has congratulatedTurkish President Recep Tayyip Erdogan after a referendum handed him the reins of Turkey's governance.
Mr Trump ignored the concerns about voting irregularities raised in several quarters.
Both Germany and France expressed concern about possible election irregularities and called on Mr Erdogan to engage in dialogue with the opposition.
The two leaders also discussed Turkey's support of the US response to a Syrian chemical weapons attack and efforts to counter the Islamic State terror group, according to the White House.
The US State Department, however, echoed the concerns raised by the OSCE, with spokesman Mark Toner pointing to "observed irregularities" on voting day and "an uneven playing field" during the campaign.
The Turkish president's victory leaves the nation deeply divided and facing increasing tension with former allies abroad, while international monitors and opposition parties have reported numerous voting irregularities.
An unofficial tally carried by the country's state-run news agency gave Mr Erdogan's Yes vote a narrow win, with 51.4pc approving a series of constitutional changes converting Turkey's political system from a parliamentary to a presidential one.
Critics argue the reforms will hand extensive power to a man with an increasingly autocratic bent, leaving few checks and balances in place.
Opposition parties called for Sunday's vote to be annulled because of a series of irregularities, particularly an electoral board decision to accept ballots that did not bear official stamps, as required by Turkish law.
Monitors from the Organisation for Security and Co-operation in Europe, who also listed numerous irregularities, said the move undermined safeguards against fraud.
The referendum campaign was heavily weighted in favour of the Yes campaign, with Mr Erdogan drawing on the full powers of the state and government to dominate the airwaves and billboards.
The No campaign complained of intimidation, detentions and beatings.
In Istanbul, hundreds of No supporters demonstrated in the streets on Monday, chanting "thief, murderer, Erdogan" and banging pots and pans.
Mr Erdogan was unfazed by the criticism as he spoke to flag-waving supporters in the capital Ankara.
"We have put up a fight against the powerful nations of the world," he said as he arrived at the airport from Istanbul.
"The crusader mentality attacked us abroad. We did not succumb. As a nation, we stood strong."
In a speech before a massive crowd at his sprawling presidential palace complex, Mr Erdogan insisted Turkey's referendum was "the most democratic election ever seen in any Western country" and told the OSCE monitors to "know your place".
The referendum was held with a state of emergency still in place, imposed after an attempted coup in July.
About 100,000 people have been sacked from their jobs in the crackdown that followed on supporters of a US-based Islamic cleric and former Erdogan ally whom the president blamed for the attempted putsch.
Tens of thousands have been arrested or imprisoned, including politicians, judges, journalists and businessmen.
The Council of Ministers decided on Monday to extend the state of emergency, which grants greater powers of detention and arrest to security forces, for a further three months. It had been due to expire April 19.
There is also the risk of increased international isolation, with Mr Erdogan appealing to patriotic sentiments by casting himself as a champion of a proud Turkish nation that will not be dictated to by foreign powers in general, and the European Union in particular.
Turkey has been an EU candidate for decades, but its accession efforts have been all but moribund for several years.
"They have made us wait at the gates of the European Union for 54 years," Mr Erdogan told his supporters at the presidential palace.
"We can conduct a vote of confidence on this as well. Would we? What did England do - they did Brexit, right?"
"Either they will hold their promises to Turkey or they'll have to bear the consequences."
Mr Erdogan has also vowed to consider reinstating the death penalty, a move that would all but end prospects of EU membership. But he insisted other nations' opinions on the issue were irrelevant to him.
"Our concern is not what George or Hans or Helga says. Our concern is what Hatice, Ayse, Fatma, Ahmet, Mehmet, Hasan, Huseyin says," he thundered as the crowd of supporters chanted for the return of capital punishment.
"What Allah says. That's why our parliament will make this decision.
The referendum approves 18 constitutional amendments to replace Turkey's parliamentary system with a presidential one.
The president will be able to appoint ministers, senior government officials and to hold sway over who sits in Turkey's highest judicial body, as well as to issue decrees and declare states of emergency. They set a limit of two five-year terms for presidents.
The new system takes effect at the next election, currently slated for 2019.