ANKARA (Reuters) - A last-minute decision by Turkey's electoral board to accept unstamped ballots as valid votes will cause a serious legitimacy problem in Sunday's referendum, the deputy chairman of the main opposition People's Republican Party (CHP) said.
A statement on the High Electoral Board's (YSK) website hours before polls closed said it would count ballots that had not been stamped by its officials as valid unless they could be proved fraudulent, citing a high number of complaints that YSK officials at polling stations had failed to stamp them.
"The High Electoral Board has failed by allowing fraud in the referendum," CHP deputy chairman Bulent Tezcan told reporters at the party's headquarters in Ankara.
Turkey's state-run Anadolu news agency said the "yes" vote in favour of constitutional changes which would boost President Tayyip Erdogan's powers stood at 59.4 percent, with around 40 percent of ballots counted.
(Reporting by Gulsen Solaker; Writing by Ece Toksabay; Editing by Nick Tattersall)