Turkey's top electoral officials have rejected petitions by opposition parties to throw out the result of a referendum on expanding the president's powers.
The country's high electoral board announced in a statement they had ruled 10-1 against the move.
On Sunday, Turkey narrowly voted to give President Recep Tayyip Erdogan sweeping new powers and replace their parliamentary system with a presidential one.
The change could potentially allow Mr Erdogan to remain in power until 2029.
The vote has been criticised by opposition parties because ballot papers which were unstamped, as required by Turkish law, were included in the count.
Opposition parties filed formal requests asking the electoral board to void the referendum result over concerns about voting irregularities.
Following the board's ruling, the Republican People's Party said it would not give up on "no" voters who opposed the changes.
The party said it planned to appeal to Turkey's constitutional court and, if it is unsuccessful there, then the European Court of Human Rights.
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Before the announcement, Prime Minister Binali Yildrim said the opposition had the right to file objections but said that calling for street protests was unacceptable.
International election monitors, including the Organisation for Security and Cooperation in Europe, have expressed concern over the way the vote was carried out.
The German government has also questioned the vote after the EU called for a probe into the result .
A government spokesperson said: "We will follow closely how Turkey behaves on this. From the German government's point of view, Turkey must ... clear up the questions that have been raised."
President Erdogan has accused people critical of the vote of "belittling the result" and warned that attempts to reverse it will "be in vain".