Erdogan had promised that his speech in Ankara would give the "naked truth" about the killing and he gave a host of new details while still saying Turkey wanted answers to key questions, including who gave the orders, AFP reported.
The murder of the Washington Post contributor has damaged the international reputation of Saudi Crown Prince Mohammed bin Salman who is now accused of having ordered Khashoggi's murder – a claim Riyadh denies.
"My demand is that 18 people be tried in Istanbul," Erdogan said in a speech to ruling party lawmakers in Ankara, referring to 18 people including security officials who have already been detained by Riyadh.
He added that "all those who played a role in the murder" had to face punishment.
Erdogan said that the murder was "planned" days in advance according to a "roadmap" set up by a Saudi team who were sent to Istanbul for the purpose. The surveillance system at the Saudi consulate in Istanbul was deactivated on purpose, he said.
Erdogan added he still wanted answers on numerous issues including "who gave orders" to the team and where the corpse is.
“The Saudi administration has taken an important step by admitting to the murder. From now on, we expect them to uncover all those responsible for this matter from top to bottom and make them face the necessary punishments,” Erdogan said.
Saudi Arabia only confirmed the killing more than two weeks after the event. The killing has alarmed even Saudi Arabia's staunchest Western allies.
A former royal family insider turned critic of the Saudi crown prince, Khashoggi, 59, disappeared after he entered the Saudi consulate in Istanbul on October 2 to collect a document for his upcoming marriage.
The timing of the controversy could not be worse for Prince Mohammed as the investment summit, dubbed "Davos in the desert", began in Riyadh, overshadowed by big name cancellations and Erdogan's threat of revelations.
Dozens of executives, including from banks Goldman Sachs and JP Morgan, ride-hailing app Uber and Western officials such as International Monetary Fund chief Christine Lagarde have pulled out of the three-day Future Investment Initiative (FII).
German Chancellor Angela Merkel said Berlin would not export arms to Riyadh "in the current situation," despite Germany's approval last month of 416 million euros' ($480 million) worth of arms exports in 2018.
Despite also pulling out of the summit, US Treasury Secretary Steven Mnuchin met the crown prince behind closed doors for bilateral talks in Riyadh. CIA Director Gina Haspel, meanwhile, headed for Turkey, although details of her trip were not immediately clear.