Demonstrators hold photographs of journalist Jamal Khashoggi outside the White House in Washington, D.C., on Friday, Oct. 19, 2018.

The Saudi public prosecutor heading the investigation into the killing of Jamal Khashoggi arrived in Istanbul overnight, the state-owned Anadolu news agency said on Monday, ahead of expected talks with the Istanbul chief prosecutor.

President Tayyip Erdogan said on Saturday that Turkey values the outcome of the talks between the two prosecutors. The timing of their meeting was not immediately clear.

Anadolu said the Saudi prosecutor would also inspect the Saudi consulate in Istanbul, where Khashoggi was killed three weeks ago.

The death of Khashoggi — a Washington Post columnist and a critic of Saudi Arabia's de facto ruler, Crown Prince Mohammed bin Salman — sparked global outrage and pitched the world's top oil exporter into crisis.

Erdogan has expressed skepticism about Saudi's shifting explanations of the killing and has called on the kingdom to hold to account all those responsible, no matter how highly placed.

Saudi public prosecutor Saud Al Mojeb said this week the killing was premeditated, contradicting a previous official statement that it happened accidentally.

Turkish prosecutors have also prepared a request for the extradition from Saudi Arabia of 18 suspects who were arrested by Riyadh as part of the investigation.

Those suspects include a 15-man security team that Turkey says flew in hours before the killing and carried it out.

Erdogan said on Saturday that the extradition request was being relayed to Saudi Arabia via Turkey's justice ministry.

Saudi Foreign Minister Adel al-Jubeir said that those behind the killing would be prosecuted in the kingdom.

Turkey has said it shared information regarding the investigation with other countries, including the United States, Germany, France and Russia.