The Turkish president has vowed to reveal the “naked truth” about the killing of journalist Jamal Khashoggi at the Saudi consulate in Istanbul.
Recep Tayyip Erdogan, who has stopped short of blaming the Saudis, is due to address members of his ruling AK party.
Turkish officials say they have evidence to show Khashoggi was murdered in the consulate on 2 October.
After weeks of conflicting accounts, the Saudis now say he was killed in a rogue operation.
Tuesday’s address by President Erdogan coincides with the start of an investment conference in Saudi Arabia that has been overshadowed by the Khashoggi case, with dozens of government and business leaders pulling out.
Many world leaders have condemned the murder of the Washington Post contributor and demanded a full investigation.
Despite the growing concern, US Treasury Secretary Steven Mnuchin held talks with Saudi Arabia’s crown prince in Riyadh on Monday.
What has Turkey already said about the killing?
Turkish officials believe Khashoggi, a prominent critic of the Saudi government, was murdered by a team of Saudi agents soon after he arrived at the consulate to obtain divorce papers nearly three weeks ago.
Investigators say they have audio and video evidence to back up this claim, and some of the lurid details have been leaked to Turkish media close to the government. However, these have yet to be made public.
They include reports that 15 suspects arrived in Turkey from Saudi Arabia hours before Khashoggi’s disappearance, and went on to dismember him with a bone saw.
Turkish police have so far searched the premises and grounds of the consulate, and the residence of the Saudi consul, as well as a nearby forest where they believe the body may have been taken.
On Monday Turkish police found a car belonging to the Saudi consulate left in a car park in Istanbul. Turkish media also posted footage apparently showing Saudi consular staff in Istanbul burning documents a day after Khashoggi’s disappearance.
Separately, CNN broadcast images appearing to show a Saudi operative leaving the consulate in Khashoggi’s clothes, wearing a fake beard and glasses on the same day he was killed.