Turkish investigators analysing phone calls and the movement of the suspects in Khashoggi’s murder have confirmed that the operation to kill the journalist was planned 12 days in advance, Al Jazeera reports.

Investigators sifting through 19 phone calls made by Maher Mutreb, thought to be the lead negotiator inside the consulate, to Saudi Arabia have found that four of them were made to Saud al-Qahtani and that there is a third voice on the calls.

Al-Qahtani was believed to be the right-hand man of Saudi Crown Prince Mohammed bin Salman before being removed as a royal court adviser following the uproar over the murder.

“Today we learned from the officials that when Mutreb and al-Qahtani were talking on the phone, there was a third voice coming from the background of al-Qahtani’s phone … Al-Qahtani was transferring the information that he got from Mutreb to that third person,” Al Jazeera’s Sinem Koseoglu, reporting from Ankara, said.

“According to Turkish officials, they strongly believe that this third voice could belong to the Crown Prince Mohammed bin Salman but the technical analysis hasn’t concluded that yet because Mutreb was doing all these calls from his Saudi mobile phone and technically Turkey needs support to analyse it properly,” she said.

It has also come to light that along with the Saudi consul-general, three other Saudi nationals employed in the consulate are considered as prime suspects in the investigation into Khashoggi’s killing.

Turkish officials say those employees fled Turkey within three days of the consul-general also leaving the country shortly after Khashoggi’s murder.

One of the employees, who is thought to be linked to the Saudi intelligence agency, travelled to Riyadh 72 hours before Khashoggi’s arrival and returned to the consulate in Istanbul just before Khashoggi.

Meanwhile, Erodgan Recep Tayyip, Turkey president. had said earlier that the killing of Khashoggi was premeditated “The information was given to the team that planned and executed the murder of the journalist, so that was the beginning of that planning phase.

“And some consular officers, officials actually left for their countries in a haste and this points in the direction that some preparation was indeed done,” he said.