Istanbul (CNN) Turkish President Recep Tayyip Erdogan is demanding that Saudi Arabia reveal the location of Jamal Khashoggi's body and hand over the suspects in his murder.

Erdogan said the top Saudi prosecutor will travel to Turkey on Sunday to meet with the top Istanbul prosecutor, and argued that those responsible for killing the journalist should face trial in Turkey.

"Whatever happened, it comes down to these 18 persons. If you are determined, if you want to remove the suspicion and clear the air, these 18 persons are the bottom line to this," Erdogan said Friday, addressing the provincial heads of his ruling Justice and Development Party in Ankara.

If the Saudis can't make the suspects talk, then Turkey will, he said. "The incident took place in Istanbul. So, hand them to us, and let us judge them," he said.

The Istanbul prosecutor's office submitted an extradition request to Saudi Arabia Friday for the 18 suspects linked to Khashoggi's death.

A senior Turkish official told CNN that "it is clear that the judicial system in Turkey is better equipped to genuinely serve the cause of justice in this case," and that court proceedings in Turkey would be open to international observers.

After Saudi Arabia admitted that Khashoggi was killed October 2 in its Istanbul consulate, five high-ranking officials were dismissed, including Saudi Crown Prince Mohammed bin Salman's media chief and the deputy head of the Saudi intelligence service. Eighteen people were arrested.

Riyadh has maintained that neither bin Salman nor King Salman knew of the operation to target Khashoggi. US officials have said such a mission -- including 15 men sent from Riyadh -- could not have been carried out without the authorization of bin Salman, the country's de facto ruler.

Turkish officials played the purported audio of Khashoggi's killing to CIA Director Gina Haspel, according to two sources familiar with Haspel's meetings in Turkey this week.

Erdogan described some of the statements made by Saudi authorities as the Khashoggi case unfolded as "very funny" and said their strangeness had increased the Turkish authorities' responsibility to act.

"These juvenile statements do not match with the seriousness of government affairs," he said. "It is obvious that (Khashoggi) is killed. But where? Where is the body?"

He also suggested that the Turkish authorities had further significant information in their possession, saying: "It's not like we don't have other documents... Tomorrow is another day."

Fiancée: He did not want to go

Khashoggi's fiancée, Hatice Cengiz, told Turkish broadcaster Haberturk on Friday that the journalist had been concerned about going to the Saudi consulate in order to obtain paperwork allowing him to remarry, fearing tensions might arise.

"Of course, he did not want to go," she said.

Journalist Jamal Khashoggi is pictured with his fiancee, Hatice Cengiz.

Nonetheless, he did not fear arrest, Cengiz told Haberturk, according to the Reuters news agency. "His local network in Turkey was very good as you know, his political network as well," Cengiz said. "He thought Turkey is a safe country and if he would be held or interrogated, this issue would be swiftly solved."

Cengiz said her expectation now was the same as Erdogan's: for those responsible for Khashoggi's death to be tried.

Speaking about an invitation she received from US President Donald Trump to visit the White House, Cengiz said, "The statements Trump made in the first days around his invite and the statements he made afterward opposed each other. They were simply statements to gain public sympathy."

She added that US Secretary of State Mike Pompeo called her a couple of days later. "I think the call was about showing that they were serious after Trump's statements," she said.

Cengiz said nobody in Saudi Arabia had called her.

In his will, Khashoggi said he wanted to be buried in the Saudi city of Medina, she said, adding that she hoped that this would happen when his body is found. Asked if she would visit him there, her response was negative.

Saudi prosecutor: Killing was 'premeditated'

News of the Saudi attorney general's planned trip to Turkey comes a day after he said that Saudi Arabia now considered Khashoggi's killing to be "premeditated," based on information from Turkish investigators.

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The statement by Attorney General Shaikh Suood bin Abdullah Al Mo'jab, posted by the state-run Saudi news agency, represented another significant shift in the Saudi version of events surrounding the Washington Post columnist's death at the Saudi consulate in Istanbul earlier this month. Riyadh initially claimed he had walked out of the consulate alive.

CIA chief Gina Haspel briefed US President Donald Trump on her findings Thursday following her trip to Turkey, where she was dispatched Monday apparently to assess information the Turks have collected on Khashoggi's killing. The Washington Post reported Wednesday that Haspel listened to audio purportedly of his interrogation and murder while she was in Turkey.

The White House confirmed the briefing had taken place but gave no further details.

The UN's Special Rapporteur on extrajudicial, summary or arbitrary executions, Agnes Callamard, said Friday that Khashoggi's killing had "all the hallmarks of an extrajudicial execution."

"And until I am proven otherwise, I will have to assume that this is the case," she said, speaking at UN headquarters in New York. "On the basis of what I know, it was an extrajudicial execution because the people involved... the people who orchestrated are high enough to represent the state. And there has been no information so far that they acted in a completely rogue fashion."

Callamard repeated a call for an international investigation to be carried out, given the nature of the crime and who the victim was.

Kremlin: No reason not to believe Saudis

The Saudi government has faced wide condemnation from western nations over Khashoggi's killing and its apparent cover-up. Russia, however, has yet to criticize the kingdom.

Kremlin spokesman Dmitry Peskov told reporters on a conference call Friday that there was no reason to doubt what Saudi Arabia's ruling royals have said about Khashoggi's death.

Asked if the Kremlin believes the statements, Peskov said: "That is an inappropriate question, there is an official statement from the King and Crown Prince. There is no reason basically not to believe it."

Russia's position has been set out by President Vladimir Putin, Peskov said. "After the statement by the royal family, about condemning this killing and on the royal family not being involved, everything else is a question for the investigation."

Putin discussed the Khashoggi case with King Salman on Thursday, in a phone call held at the initiative of the Saudi side, the Kremlin said.

On the same day, Russia's sovereign wealth fund announced plans to bring in Saudi Arabia's sovereign wealth fund as a new partner in its joint Russia-China Investment Fund.

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France: No sanctions for now

French President Emmanuel Macron said arms sales have "nothing to do with Mr. Khashoggi" and that the two issues should not be confused during a press conference in Bratislava, where he was visiting his Slovak counterpart on Friday.

Macron later added that "It is pure demagoguery to say stop selling arms" to Riyadh and pleaded for "a European response, in all areas," but "once facts are established."

Macron again reiterated these points in a series of tweets in which he condemned the killing of Khashoggi. Later, he added that he doesn't "believe in outburst and confusion" and that "once a light is shone on this crime, we will take clear, coherent and coordinated sanctions at the European level."

On Sunday, German Chancellor Angela Merkel announced that her country will halt all exports of weapons to Saudi Arabia while uncertainty surrounds Khashoggi's death.