The Daily Sabah newspaper reported, citing Istanbul's Chief Public Prosecutor Irfan Fidan, that the investigation into Khashoggi's death had been completed.
Following an investigation of more than a year into the assassination of journalist Jamal Khashoggi in Istanbul in 2018, Turkey announced on Wednesday March 25 that it has launched proceedings against 20 Saudi nationals, including two close to the prince heir Mohammed ben Salmane.
According to state news agency Anadolu, the other two defendants have been charged with incitement of first degree murder.
The kingdom's deputy intelligence chief Ahmed al-Assiri and royal court adviser Saud al-Qahtani are accused of leading the operation and giving orders to a hit team to kill the Washington Post columnist.
Twenty Saudi nationals have been indicted by the Istanbul prosecutor's office, of being involved in the killing of the journalist, who often criticised Saudi royalty.More news: The Mandalorian: Michael Biehn To Play A Bounty Hunter
Turkey's ties with Saudi Arabia have come under strain since the brutal murder last October of Khashoggi in the Saudi consulate in Istanbul, which tarnished the worldwide reputation of the crown prince.
The killing shone a light on the extraordinary crackdown on dissent carried out by Saudi authorities under Mohammed's leadership and soured relations between Saudi Arabia and Turkey.
A United Nations probe revealed that Saudi government agents had discussed murdering and dismembering Khashoggi before his arrival at the building, referring to the journalist as "the sacrificial animal".
Fidan's office said the 18 suspects are accused of "acting in consensus from the beginning in line with the decision of taking the victim back to Saudi Arabia and of killing him if he did not agree".More news: Google Podcasts App May Be Coming Soon to iOS With Refreshed Design
The gruesome killing shocked the world and UN Special Rapporteur Agnes Callamard said there was credible evidence that Crown Prince Mohammed and other high-level Saudi officials were individually liable.
The statement did not provide further details, and it was not immediately clear whether the suspects would be tried in absentia.
Five people were sentenced to death while three other people were found guilty of covering up the crime and were sentenced to a combined 24 years in prison.
The Istanbul prosecutor's office said in a statement that Assiri and Qahtani were charged with "instigating the deliberate and monstrous killing, causing torment". As global pressure mounted because of the Turkish leaks, the kingdom eventually settled on the explanation that he was killed by rogue officials in a brawl.More news: Here’s what’s in the new $2 trillion coronavirus aid bill