Saudi Arabia's Crown Prince Mohammed bin Salman has described the killing of Jamal Khashoggi as a "heinous" crime, in his first comments since some of his closest aides were implicated in the Saudi journalist 's death.

Speaking at an investors’ conference Riyadh that has been overshadowed by the crisis, bin Salman said those responsible for the killing would be brought to justice.

“This was a very, very painful incident for all Saudis and also for everybody on this planet. It was unnecessary,” he said.

The crisis has presented a threat to bin Salman in a way that a bloody war in Yemen, the alleged abduction of the Lebanese Prime Minister, and a crackdown on dissent at home, have not. After Saudi Arabia admitted at the weekend that Khashoggi was killed in its Istanbul consulate on October 2, five high-ranking officials were dismissed, including bin Salman’s media chief and the deputy head of the Saudi intelligence service. In total, 18 people were arrested.

Riyadh has maintained that neither bin Salman nor his father, 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.

“Saudi Arabia will go and implement all necessary rules and investigate deeply in order to achieve results. And to bring to justice those who are responsible for this heinous crime, and they will be put before courts,” bin Salman told his audience in Riyadh Wednesday.

In its public admission at the weekend, Saudi Arabia claimed that Khashoggi died when a discussion turned violent. In private, officials have offered a shifting narrative — in the latest version offered by an official, the original plan was to persuade Khashoggi to return to Saudi Arabia, and if he refused, to drug him and take him to a safe house in Istanbul. But Khashoggi became agitated, the official claimed, and he died in a chokehold.

Turkey has rejected the notion that the Khashoggi fell victim to a rogue operation. President Recep Tayyip Erdogan described his death on Tuesday as a “ferocious” premeditated murder. Speaking Wednesday at the presidential palace in Ankara, Erdogan once again made clear that he was not satisfied with the Saudi explanation.

“We are determined not to allow those responsible — those who ordered the crime and those who committed it — to escape justice,” he said.

Bin Salman insisted that good working relations between Saudi Arabia and Turkey should not suffer as a result of the crisis. “We will be sure to see that we cooperate with each other, that justice will be done,” he said.

Earlier Wednesday, Bin Salman and Turkish President Recep Tayyip Erdogan discussed the journalist’s killing in a phone call, according to Turkey’s state news agency Anadolu and the Saudi Press Agency. Bin Salman requested the call to discuss a joint effort to shed light on all aspects of the death, Anadolu reported, citing Turkish presidential sources.

In the latest iteration of a shifting story, Saudi officials told CNN that the original plan was to convince Khashoggi, who had been writing critical columns in the Washington Post, to return to Saudi Arabia. If Khashoggi refused, an official said, the next step was to drug him with a tranquillizer and take him to a safe house in Istanbul for 48 hours. If Khashoggi still refused to return to Saudi Arabia at that point, the team was to leave and a “local collaborator” was to let him go, the source claimed.

The Saudi official also claimed that a forensic expert was present to erase all evidence of Khashoggi’s presence at the consulate and safe house so that if Khashoggi said later that he had been kidnapped, there would be no proof.

The official has provided no corroborating evidence for this new version of events. The New York Times has reported that the forensic expert was equipped with a bone saw.

They said that of the 15 Saudis who took part in the operation, a total of nine were at the consulate, with “three or four to question him and the rest to handle logistics.” There was no explanation why three to four people would be needed for questioning, or what logistics the others would attend to.

The rest of the 15-man team that Turkey said was a hit squad, including generals and their security detail, waited at the safe house, according to the source.

Turkish officials have said that Khashoggi was set upon immediately after entering the consulate, and then beaten, tortured and dismembered.