The Organisation for Security and Cooperation in Europe (OSCE) has charged in a damning report that Turkey's election was marred by a media crackdown, violence and other security concerns.
It said on Monday that the campaign for Sunday's vote was characterised by "unfairness" and "fear" after a surge in violence.
The election delivered a clear victory to the Justice and Development Party (AKP) of President Recep Tayyip Erdogan, a dramatic turnaround after it lost its parliamentary majority in June.
"While Turkish citizens could choose between genuine and strong political alternatives in this highly polarised election, the rapidly diminishing choice of media outlets, and restrictions on freedom of expression in general, impacted the process and remain serious concerns," Ignacio Sanchez Amor, special coordinator and leader of the OSCE observer mission, said in a statement.
Concerns over media freedoms were already running high in the run-up to the poll after riot police last week stormed the Ankara and Istanbul offices of two television stations critical of the Turkish strongman.
"Physical attacks on party members, as well as the significant security concerns, particularly in the southeast, further imposed restrictions on the ability to campaign," Amor added.
A massive suicide bombing on a peace rally in Ankara last month killed 102 people in the worst attack in the country's history, with political parties temporarily suspending campaigning.
"Unfortunately, the campaign for these elections was characterised by unfairness and, to a serious degree, fear," said Andreas Gross, head of the Parliamentary Assembly of Council of Europe (PACE) delegation.
He called on Erdogan to work for an "inclusive political process" to deal with challenges facing Turkey.
The elections were also held against a backdrop of a military campaign against Kurdish rebels in the southeast of Turkey and in northern Iraq after attacks on security forces by the militants.
Observers said the army's operations in the Kurdish-dominated southeast hampered the ability of the pro-Kurdish Peoples' Democratic Party (HDP) to campaign.