Saudi Arabia's powerful Crown Prince Mohammed bin Salman vowed on Wednesday that the killers of Jamal Khashoggi would be brought to justice.

Prince Mohammed told international investors at a major conference in Riyadh that the furore over Khashoggi's killing at the Saudi consulate in Istanbul would not derail the kingdom's reform drive.

"We will prove to the world that the two governments (Saudi and Turkish) are cooperating to punish any criminal, any culprit and at the end justice will prevail," Prince Mohammed said to applause.

Prince Mohammed said Saudi Arabia and Turkey would work together "to reach results" on a joint investigation and described cooperation between the two countries as "special", despite criticism from Ankara.

"The incident that happened is very painful, for all Saudis... The incident is not justifiable," the crown prince said on a discussion panel at the conference.

Erdogan spoke to Prince Mohammed on Wednesday and the two discussed the steps needed to bring to light all aspects of Khashoggi's death, a presidential source said.

"There are now those who are trying to take advantage of the painful situation to create a rift between the kingdom and Turkey," he said.

"I want to send them a message that they cannot do this as long as there a king named Salman bin Abdulaziz and a crown prince named Mohammed bin Salman in Saudi Arabia, and a president in Turkey named Erdogan."

France said on Wednesday it could impose sanctions on Saudi Arabia if its intelligence services establish that the kingdom was behind Khashoggi's murder, although government spokesman Benjamin Griveaux said there would be no hasty conclusions.

The Future Investment Initiative conference in Riyadh was overshadowed by Khashoggi's killing, with more than two dozen high-level participants withdrawing.

But Saudi Arabia showed it could still do business despite the furore, signing deals worth $50 billion at the conference on Tuesday. The event was attended by hundreds of bankers and company executives.

Prince Mohammed, 33, was upbeat on the economy, predicting growth of 2.5 percent this year.

He seemed relaxed on the panel he shared with Bahrain's Crown Prince Salman bin Hamad al-Khalifa and Lebanon's Prime Minister Saad al-Hariri. He joked about Hariri's detention in the kingdom last year, saying the Lebanese prime minister was free to leave after attending the conference.

"Prime Minister Saad is staying in the kingdom for two days so I hope you don't spread rumours that he was kidnapped," Prince Mohammed said.

The Saudi central bank governor sought to reassure foreign banks that withdrew from the conference that they would not be penalised and may apply for licenses to operate in the country, the Middle East's largest economy.

During the panel Prince Mohammed touted Saudi Arabia's success in its efforts to transform its oil-dependent economy and make the deeply conservative kingdom a more tolerant society.

"All our projects are going ahead, reform is going ahead, our war on extremism is going ahead, our war on terrorism is going ahead...our efforts won’t stop no matter how they try to constrain us," he said.

Lucid Motors chief technology officer Peter Rawlinson was also present and the U.S. company had a dedicated stand at the venue. In September Saudi Arabia's Public Investment Fund agreed to invest more than $1 billion in Lucid as part of Saudi efforts to diversify the oil-dependent economy.