Turkey’s main opposition party CHP has called for the annulment of the referendum held on April 16 on constitutional amendments that will create an executive presidential system.

The CHP has received complaints from many regions that people had been unable to vote in privacy and said that some ballots were counted in secret, the party’s deputy chairman Bulent Tezcan said on April 17, Reuters reported.

The High Electoral Board's (YSK) decision to accept unstamped ballots was clearly against the law, he added.

Earlier on April 17, the head of the electoral board said ballots and envelopes provided to voters for the referendum were produced by the YSK and were valid, Hurriyet Daily News reported.

“At the moment it is impossible to determine how many such (unstamped) votes there are and how many were stamped later. This is why the only decision that will end the debate about the legitimacy (of the vote) and ease people's legal concerns is the annulment of this election by the YSK,” Tezcan said, according to Reuters.

“We take note of the reported results of the referendum in Turkey on the amendments to the Constitution. We are awaiting the assessment of the OSCE/ODIHR International Observation Mission, also with regard to alleged irregularities,” the European Commission said in a statement on April 16.

The US has also said it won’t comment on the result of the referendum until the OSCE releases its report, Hurriyet Daily News reported.

The international observers monitoring the constitutional referendum will present their preliminary post-referendum statement at a news conference on 17 April the OSCE announced in a statement on its website.