Last month, a court in Saudi Arabia issued final verdicts convicting eight unnamed Saudi nationals in Khashoggi's 2018 killing.
The six Saudi suspects, indicted just days ahead of the second anniversary of the journalist's death, are not in Turkey and should be tried in absentia.
The court ordered a maximum sentence of 20 years in prison for five, another received a 10-year sentence, and two others were ordered to serve seven years in prison.
Khashoggi -- a royal family insider turned critic -- was killed and dismembered at the kingdom's consulate in Istanbul in October 2018.
Prosecutors accuse Saudi Arabia's deputy intelligence chief Ahmed al-Assiri and the royal court's media czar Saud al-Qahtani of leading the operation, and giving orders to a Saudi hit team.
All suspects in the killing have left Turkey and Saudi Arabia has put 11 people on trial over the murder.
Khashoggi -- a royal family insider turned critic -- was killed and dismembered at the Saudi consulate in Istanbul on October 2, 2018.
The Saudi crown prince, Mohammed bin Salman, had drawn international condemnation for the killing because several Saudi agents involved worked directly for him.
Khashoggi, a Washington Post contributor and US resident, was killed in October 2018 by Saudi agents while at Saudi Arabia's consulate in Istanbul to obtain paperwork ahead of his wedding.
The Saudi Media Forum is hosting more than 1,000 journalists from Arab and international media, in a first such conference focused on 'opportunities and challenges' in the industry.
The news came hours after police confirmed that around 15 Saudis, including officials, arrived in Istanbul on two flights on Tuesday and were at the consulate at the same time as the journalist.