Before the electoral board's announcement, Prime Minister Binali Yildirim said that the opposition had the right to file objections, but warned that calling for street protests was unacceptable.
The main opposition Republican People's Party (CHP) and the pro-Kurdish Peoples' Democratic Party (HDP) had Tuesday requested the poll be scrapped due to alleged violations. Worldwide observers said the vote had been carried out in a political environment in which fundamental rights and freedoms had been curtailed.
CHP party leader Kemal Kilicdaroglu also accused the electoral board of bias and favoring Erdogan's party.
Sancar went on to state that the electoral board's last-minute decision to allow unstamped ballots had prevented proper record-keeping to occur, meaning it was now impossible to determine how many invalid or make votes may have been counted.
ISTANBUL (AP) - Turkey's electoral board on Wednesday rejected petitions by opposition parties to annul the outcome of a recent referendum on expanding presidential powers because of voting irregularities.
Unofficial results show a narrow win for President Recep Tayyip Erdogan's "Yes" campaign, which won 51.4% of the vote.
The U.S. State Department said it had taken note of the European monitors' concerns and looked forward to a final report, urging the Turkish government to protect the rights and freedoms of all citizens, however they voted.
The referendum asked voters to choose "yes" or "no" on 18 constitutional amendments, one that will see the country switch from a parliamentary to a presidential system.
"The main opposition party not recognizing the results is not an acceptable thing", Yildirim said.
Global election monitors, including from the Organization for Security and Cooperation in Europe, noted a series of irregularities, and said the decision to accept as valid ballots without official stamps undermined safeguards against fraud and was contrary to Turkish law.
A defiant Erdogan has dismissed complaints from his domestic opponents and European observers, saying the vote put to an end all debate over the powerful presidency he has long sought.
"We will determine a date for the two presidents to meet in May before the North Atlantic Treaty Organisation summit as previously confirmed by the leaders", Foreign Minister Mevlut Cavusoglu tells reporters in Ankara.
Turkish Foreign Minister Mevlut Cavusoglu responded to the report earlier on Wednesday, saying it has "no reliability as their observations lack objectivity and are extremely partial".