Ten out of 11 board members voted against the appeals last week after the petitions were filed by main opposition Republican People’s Party (CHP), Peoples’ Democracy Party (HDP) and the left-wing Patriotic Party.
The board said in a statement that it had decided to accept unstamped ballot papers before the boxes were closed for vote counting, adding that the decision was objective, and in line with the principle of equality and impartiality.
"In accordance with the requirements of a democratic society, the right of citizens to participate in governance by voting should be protected against all kinds of obstacles.
"For this reason, citizens' right to vote is a right that must be protected in cases where it does not violate election security," the statement said.
The YSK stressed that the mistakes of the ballot box officials who did not stamp the ballot papers in certain locations should not obstruct the people's rights to vote.
After the election board rejected the opposition parties' appeal, the CHP then approached the Council of State, urging the court to suspend the official referendum results until the end of the legal process.
However, the court also rejected the appeals saying no appeal against YSK decisions could be made at any court.
Turkey’s main opposition party said that it would appeal the results of the referendum at the European Court of Human Rights (ECHR).
The election board has announced late Thursday the official referendum results, declaring a 'Yes' wins with 51,41 percent while 48,59 percent voted against the constitutional change in Turkey.
YSK President Sadi Guven said in a press conference in Ankara that 25,157,463 people had voted 'Yes' while 23,779,141 voted 'No'.
Voter turnout was 87.45 percent, he said.
The vote was organized to determine whether to approve changes to the country’s constitution that will usher in an presidential system of governance.