Turkey's referendum campaign was conducted on an "unlevel playing field" and the vote count itself was marred by late procedural changes that removed key safeguards, international observers said on Monday, April 17, Reuters reports.

Turkey voted on Sunday in a referendum on granting President Recep Tayyip Erdogan extra powers that was won by the 'Yes' camp but disputed by the opposition.

"The referendum took place on an unlevel playing field and the two sides of the campaign did not have equal opportunities," said Cezar Florin Preda of the joint mission of the OSCE Office for Democratic Institutions and Human Rights (ODIHR) and the Parliamentary Assembly of the Council of Europe (PACE).

"Late changes in counting procedures removed an important safeguard," said Preda, who headed the PACE delegation, referring to the election authorities' decision to permit ballot papers without an official stamp.

"The legal framework, which is focused on elections, remained inadequate for the holding of a genuinely democratic referendum," the monitors said in a joint statement.

Preda also said the fact that the referendum was held under a state of emergency imposed in the wake of last year's failed coup infringed upon a "fundamental freedom".