A defiant Mohammed bin Salman, the crown prince of Saudi Arabia, on Wednesday called the killing of Jamal Khashoggi a “heinous crime that is painful to all Saudis”, but vowed that the diplomatic firestorm would not derail his plans to encourage foreign investment into the kingdom.

In his first public comments since the murder of the dissident journalist at the Saudi embassy in Istanbul, the crown prince added: “All legal things [are being done] to finalise the investigation to cooperate with the Turkish government, to present the perpetrators to the court.”

“Some are using it to drive a wedge between Saudi and Turkey. They will not be able to do that as long as there is a king called King Salman and a crown prince called Mohammed bin Salman in Saudi Arabia, and a president in Turkey called Erdogan.

“This wedge will not happen. All perpetrators will be taken to court.”

Crown Prince Mohammed was speaking at the Future Investment Initiative (FII) in Riyadh, an event organised by the Saudi sovereign wealth fund and dubbed “Davos in the Desert”, designed to encourage foreign investment in the kingdom.

The audience appeared to be packed with supporters of the crown prince who loudly clapped and cheered his statements.

Mohammed appeared alongside the crown prince of Bahrain, Salman bin Hamad al Khalifa and the prime minister of Lebanon, Saad al-Hariri.

In response to a plea from the Bahraini ruler for foreign investors to continue to invest in the region Mohammed said: “Your royal highness, don’t worry: we have $50bn (£39bn) US dollars as of yesterday.”

This was a reference to various foreign investment pledges from western energy and infrastructure companies made earlier in the week.

Reuters reported that Mohammed and President Erdogan had spoken earlier on Wednesday about the investigation into the killing. But despite the claims of solidarity with Turkey, the government in Istanbul has been piling the pressure on Riyadh over the death.

And on Tuesday Donald Trump called the Saudi response to the murder “the worst cover-up” in history. He also indicated that he would acquiesce in any sanctions put forward by Congress.

Asked in the Oval Office how the killing of Mr Khashoggi could have happened, Mr Trump said: “They had a very bad original concept. It was carried out poorly, and the cover-up was one of the worst in the history of cover-ups.”

And in a separate interview with the Wall Street Journal, the president said he thought the crown prince could have been personally behind the killing.

“Well, the prince is running things over there more so at this stage. He’s running things and so if anybody were going to be, it would be him,” he said.

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Dozens of western business leaders and politicians pulled out of the FII conference, organised by the country’s sovereign wealth fund, in the wake of the murder of Mr Khashoggi on 2 October.

An official Saudi investigation into the disappearance of Mr Khashoggi stated last week that he had died after a “fist fight” in the embassy and that 18 Saudi nationals had been arrested.

The country’s deputy intelligence chief Ahmad al-Asiri and Saud al-Qahtani, a senior aide to the crown prince, were sacked.

The Saudis had previously insisted that Mr Khashoggi had left the embassy safely.

Theresa May said in parliament on Wednesday that the visas of the Saudi suspects would be revoked.

The FII conference, which is in its second year, was conceived by the crown prince, the de facto political leader of Saudi, as a crucial element of his long term programme to diversify the domestic economy away from its overwhelming reliance on oil.

The conference is being held at a site next to the Ritz-Carlton hotel in Riyadh, where dozens of wealthy Saudis were detained last year as part of the crown prince’s anti-corruption drive.