Erdogan to meet Trump on May 16-17 in Washington

Turkey's main opposition CHP party said on Friday it was making a court appeal against the decision by the High Electoral Board (YSK) to accept unstamped ballots in the tightly contested referendum granting President Tayyip Erdogan wide new powers.

Bulent Tezcan, a deputy chairman of the Republican People's Party, or CHP, told reporters the party was asking the Council of State to overturn the electoral board's controversial decision on the unstamped ballot papers.

"We don't and won't recognise this referendum result", the party's spokeswoman, Selin Böke, said, adding that the CHP would exercise all its democratic rights including the possibility of "seceding" from parliament.

In the last few months of Barack Obama's presidency, relations between the North Atlantic Treaty Organisation allies hit a rough patch with Turkey furious over United States backing for a Kurdish militia in Syria it sees as a terror group.

He added the CHP meant to employ all legal ways to challenge the result, including Turkey's Constitutional Court as well as European Court of Human Rights.

"This is over. The people have decided and the national will has made its voice heard", he told television news station A Haber late on Thursday. The minister went on to say that those willing to annul the results could "also apply to the ECHR, but [they] cannot achieve a result there either, because the agreements Turkey signed do not give parties the right to apply".

With Turkish police beginning to crack down on those who have called for demonstrations over the result, left-wing website sendika.org said its editor-in-chief Ali Ergin Demirhan was held in a pre-down raid on its offices.

For his part, Prime Minister Binali Yildirim said the opposition should now prepare for the next elections in 2019 instead of staging demonstrations and protests, "which would change nothing in the results" of the referendum.

Metin Feyzioglu, head of the Union of Turkish Bar Associations, said the decision to count un-stamped ballots, without keeping any record of them, removed the main safeguard against voting fraud.

Unofficial results show Erdogan's "yes" campaign garnered 51.4 percent of the vote.

Earlier this week, Turkey's electoral board rejected petitions by opposition parties to annul the outcome of the weekend's referendum on expanding presidential powers because of voting irregularities.

In this Monday, April 3, 2017 photo, banners showing modern Turkey's founder Mustafa Kemal Ataturk, left, and Turkey's current President Recep Tayyip Erdogan, right, decorate a building as people watch Erdogan's speech, during a rally for the upcoming referendum, in his hometown city of Rize, in the Black Sea region, Turkey.