Ankara, April 17 (IANS): Turkey's main opposition party on Monday announced that it would be seeking annulment of the referendum on constitutional reforms.

Vice President of the social-democratic Republican People's Party (CHP), Bulent Tezcan, said there were widespread irregularities registered in Sunday's vote, Efe news reported.

Preliminary results suggested that some 51.4 per cent of the Turkish electorate on Sunday voted in favour of a series of constitutional reforms that would see most executive power handed to the office of the President.

At a press conference at the party headquarters in Ankara, Tezcan said the only possible solution to the debates over the referendum's legitimacy were for it to be cancelled by the electoral council.

He alleged that in many places, primarily in the east of the country where the Kurdish population is concentrated and polling stations close earlier, votes were counted secretly, without impartial observers or opposition representatives present.

Opposition members had already promised to challenge some 2.5 million votes they considered suspicious, which could successfully overturn the results as the "Yes" side had won by only 1.25 million votes.

The head of the electoral council, Sadi Guven, on Monday rejected the claim that these ballots could be fake, though they were not stamped by polling station officials.

Tezcan promised that his party would take the case to the constitutional court if the electoral council did not react.

He said he was even willing to appeal to the European Court of Human Rights.

The referendum's reforms are expected to come into effect by 2019, replacing the current parliamentary system with one that would see all executive powers handed to the President's office.