"Media bias and ongoing restrictions to freedom of expression created an unlevel playing field, and contributed to an unjustified advantage of the incumbent," the OSCE said on Monday.
International observers noted on Monday that both the first round on 14 May and the run-off on 28 May in Turkey's elections were free but not fair.
While the run-off offered voters a choice between genuine political alternatives, Organization for Security and Co-operation in Europe (OSCE) Special Coordinator, Farah Karimi, said during a news conference in Ankara that “biased media coverage and a lack of a level playing field gave an unjustified advantage to the incumbent.”
Some 90% of Turkey’s media is in the hands of the government or its backers, according to Reporters Without Borders, ensuring overwhelming airtime for President Recep Tayyip Erdogan, who won re-election on Sunday.
Only a handful of opposition newspapers remain in print, most having transitioned to online-only editions.
Erdogan received nearly 33 hours of airtime on the main state-run TV station, according to opposition members of the broadcasting watchdog, while his presidential opponent, Kemal Kilicdaroglu, received 32 minutes.
Frank Schwabe, PACE (Parliamentary Assembly of the Council of Europe) head of the delegation, called for an end to speeches against minorities following the election and transparency in Turkey's electoral procedures.
Erdogan extends his increasingly authoritarian rule into a third decade as the country reels from high inflation and the aftermath of a devastating earthquake.
A third term gives him an even stronger hand domestically and internationally, and the election results will have implications far beyond the capital of Ankara.
Turkey stands at the crossroads of Europe and Asia, and it plays a key role in NATO.