The Turkish referendum result has been thrown into doubt by accusations of election fraud
As many as 2.5 million votes supporting the raft of new powers for the controversial leader may have been tampered with, according to international observers.
President Erdogan has already furiously dismissed these claims and warned foreign watchdogs to “know their place”.
The Organisation for Security and Cooperation in Europe (OSCE) say Turkish authorities are refusing to cooperate with their efforts to investigate claims of election fraud.
The mission of observers from the 47-member Council of Europe, the continent's leading human rights body, had already pronounced the referendum to be an uneven contest.
Turkey voted in favour of giving the president new powers
Support for the 'Yes' side dominated campaign coverage, and the arrests of journalists and closure of media outlets silenced other views, according to monitors.
Now the actual voting process itself is under suspicion, according to Alev Korun, an Austrian member of the Council's observer team.
'No' protestors have accused the 'Yes' campaign of election fraud
She said: “This is about the fact that actually the law only allows official voting envelopes. The highest election authority decided however – as it were, against the law – that envelopes without official stamp should be admitted.
"There is a suspicion that up to 2.5 million votes could have been manipulated.”
A look back on the shocking Turkish military coup that left 294 dead
Wed, July 27, 2016
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The violent military coup to overthrow Turkey's President Erdogan has 'failed' leaving at least 104 dead and more than 1,500 wounded
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A police officer talks with the soldiers involved in the coup attempt after they surrendered
Turkish election authorities said preliminary results showed 51.4 percent of voters had backed sweeping new powers for Erdogan, something he says is needed to prevent instability.
However, Michael Georg Link, who headed the OSCE observer mission, said Mr Erdgoan’s crackdown was motivated by a desire to gain more power in Turkey.
He said: “Erdogan's decision to extend the state of emergency for 90 days and comments in which the election commission has already rejected claims of manipulation send a clear message."
Erdogan has cracked down on freedom of speech and opponents since a deadly attempted coup last year
President Erdogan has been cracking down of opposition and critics with controversial force since a bloody attempted coup in July last year.
Hundreds of innocent civilians died during the military putsch, prompting a furious response across the country.
President Erdogan has used this fury to legitimise a crack down on enemies both real and imagined and to remove dissenters and threats to his power.