Turkish authorities have opened legal proceedings against three people who attempted to cast fraudulent votes for the pro-PKK Peoples' Democratic Party (HDP) in eastern Turkey's Ağrı province.
Legal proceedings have also be opened against an HDP observer who allegedly abetted the fraud attempt.
The accused attempted to cast votes using forged ballot papers, which they presumably copied from the internet, according to a statement.
Officials identified the fake papers as they were not carrying a seal by the election council.
"Legal proceedings have been initiated against the people who attempted to cast the fake ballot papers and an HDP observer who stealthily placed the fake ballot papers into their pockets," said the governor's office.
In the Suruç district of southeast Şanlıurfa, four people were arrested for alleged vote rigging.
During the election day, official delegations from the Organization for Security and Cooperation (OSCE), Parliamentary Assembly of the Council of Europe (PACE) and Shanghai Cooperation Organization (SCO) will monitor voting procedures such as counting, casting and recording votes without interrupting polling boards.
The observers will prepare a report by monitoring the campaigning process, on election participation and on whether international election standards were upheld.
Six candidates are contesting at the Turkish presidential race while eight political parties, including two alliances, are taking part in the parliamentary elections.
President Recep Tayyip Erdoğan runs for re-election as the candidate of the People's Alliance, formed by the ruling Justice and Development Party (AK Party) and the opposition Nationalist Movement Party (MHP). Other candidates in the presidential election race are main opposition Republican People's Party's (CHP) Muharrem Ince, newly formed Good (IYI) Party Chairwoman Meral Akşener, the Felicity Party's (SP) Temel Karamollaoğlu, the Patriotic Party's (VP) Doğu Perinçek and the pro-PKK Peoples' Democratic Party's (HDP) Selahattin Demirtaş.