Saudi Arabia has admitted journalist Jamal Khashoggi is dead.

The results of the country's own investigation were revealed Friday evening and showed the 60-year-old died following an altercation at the kingdom's consulate in Istanbul, Turkey October 2.

Saudi's attorney general said in a statement: 'Discussions between citizen Jamal Khashoggi and those who met him while he was in the Saudi Consulate in Istanbul led to a brawl and a fist fight, which led to his death.'

'The investigations are still underway and 18 Saudi nationals have been arrested,' the state prosecutor said in a statement to media. 'The kingdom expresses its deep regret.'

All are Saudi nationals.

The Middle Eastern country thanked Turkey for its 'exceptional cooperation' in the investigation.

Saudi Arabia said the suspects went to Istanbul to meet with Khashoggi over the possibility of him returning to the country.

His death occurred after a heated discussion turned into a quarrel and then a fist fight.

It has not been detailed exacted how he died.

Deputy intelligence chief Ahmed Assiri has been fired after the country's own investigation.

Saud al-Qahtani, the royal court adviser, has also been ousted.

According to CBS News the man was very close to the country's crown prince.

'You don't get much closer,' a source told Kylie Atwood.

The country is to restructure its intelligence agencies after the killing of Khasshoggi, under King Salman Abdulaziz Al Saud's orders.

Salman - who is the Custodian of the Two Holy Mosques, Al-al-Haram (in Mecca) and Al-an-Nabawi (in Medina) - ordered that a ministerial committee is formed to restructure the General Intelligence Presidency, modernize its regulations and define its powers.

The Ministry of Foreign Affairs said it was a resolutions concerning the journalist's death and is an extension of the Kingdom's commitment to consolidating justice.

However the mission is said to be led by his son Crown Prince Mohammed bin Salman, who was suspected of being behind Khasshoggi's disappearance in some versions of stories alleging what happened to the Washington Post writer.

Former British spy Sir John Sawers said Friday to BBC Radio 4 show, World at One: 'All the evidence points to it being ordered and carried out by people close to Mohammed bin Salman.

'I don’t think he would have done this if he hadn’t thought he had licence from the US administration to behave as he wished.' 

Sawers, who headed MI6 between 2009 and 2014, said he had based his assessment on conversations with sources in Whitehall coupled with his understanding of Turkey's intelligence services.

Official sources say the Kingdom is taking all the necessary steps to find out more about the circumstances under which Khasshoggi died.

The person close to the investigation said the leaders are making sure those involved are brought to justice.

It had been earlier reported that King Salman was personally intervening in the Khashoggi case after being kept in the dark about the crisis by his powerful son's aides.

Initially the king, who has handed the day-to-day running of Saudi Arabia to his son, commonly known as MbS, was unaware of the extent of the crisis, according to two of the sources with knowledge of the Saudi royal court. That was partly because MbS aides had been directing the king to glowing news about the country on Saudi TV channels, the sources said.

Since he acceded to the throne in January 2015, the king has given MbS, his favourite son, increasing authority to run Saudi Arabia. But the king's latest intervention reflects growing disquiet among some members of the royal court about MbS's fitness to govern, five sources said.

MbS, 33, has implemented a series of high-profile social and economic reforms since his father's accession, including ending a ban on women driving and opening cinemas in the conservative kingdom.

But he has also marginalized senior members of the royal family and consolidated control over Saudi's security and intelligence agencies.

His reforms have been accompanied by a crackdown on dissent, a purge of top royals and businessmen on corruption charges, and a costly war in Yemen.

Kahasshoggi had been missing 17 days after entering the consulate to obtain documents for his upcoming wedding. His partner waited outside for hours but never saw him again after he walked in at 1.14pm.

Khashoggi was a critic of Saudi Crown Prince.

The comments from Saudi on Friday evening marked the first time since Khashoggi went missing that the Saudis admitted to his death.

Turkish officials had said they believed he was killed in the building. Saudi Arabia had previously denied the allegations and said Khashoggi had left the building shortly after.

Before the Saudi announcements, US President Donald Trump said he might consider sanctions against Saudi Arabia over the disappearance , while emphasizing the importance of the US-Saudi relationship.

In Istanbul, Turkish prosecutors investigating Khashoggi's disappearance questioned Turkish employees of the Saudi consulate Friday, widening the hunt for clues in a case straining Riyadh's alliance with Western powers.

Turkish police searched a forest on Istanbul's outskirts and a city near the Sea of Marmara for Khashoggi's remains, two senior Turkish officials told Reuters, after tracking the routes of cars that left the consulate and the consul's residence on the day he vanished.

Investigators have recovered samples from searches of both buildings to analyze for traces of Khashoggi's DNA.

Speaking to reporters in Scottsdale, Arizona, Trump said it was too early to say what the consequences for the incident might be, but that the US Congress would be involved in determining the American response.

Asked whether Saudi sanctions were one of the measures he was considering, Trump said, 'Could be, could be,' though he provided no details.

'We're going to find out who knew what when and where. And we'll figure it out,' Trump added.

The US Congress is controlled by Trump's fellow Republicans, some of whom have called for tough action against Saudi Arabia.

'I will very much listen to what Congress has to say. They feel very strongly about it also,' Trump said.

Trump, who said on Thursday he believes Khashoggi is likely dead and has warned of a potential 'very severe' response, has appeared unwilling to distance himself too much from the Saudis, citing Riyadh's role in countering Iranian influence in the Middle East and lucrative potential arms deals.

'Saudi Arabia has been a great ally, they've been a tremendous investor in the United States,' Trump said, adding, 'That's why this is so sad.'

'They agreed to spend $450 billion on buying in and investing in the United States, so I hope we can keep that open. ... There are plenty of other things we can do,' he said, adding, 'I might know a lot by Monday. I know a lot already.'

State-run Anadolu news agency said the Turkish prosecutor's office had obtained testimony from 20 consulate employees, and 25 more people including foreign nationals would be questioned.

The consulate employees questioned included accountants, technicians and a driver, Anadolu said. The investigation is being conducted by the prosecutor's terrorism and organized crime bureau, it added.

Turkey said it had not shared with any country audio recordings purportedly documenting Khashoggi's murder inside the consulate, dismissing reports it had passed them to the United States.

'We will share the results that emerge transparently with the whole world,' Turkish Foreign Minister Mevlut Cavusoglu said.

Turkish pro-government newspaper Yeni Safak has published what it said were details from the audio, including that his torturers severed Khashoggi's fingers during an interrogation and later beheaded and dismembered him.

Khashoggi's disappearance has tarnished the crown prince's reputation and deepened questions about his leadership, prompting Saudi King Salman to intervene, five sources with links to the Saudi royal family told Reuters.

The crown prince has painted himself as the face of a vibrant new kingdom, diversifying its economy away from oil and introducing some social changes. Other moves have faced criticism, including involvement in Yemen's war, the arrest of women activists and a diplomatic dispute with Canada.

U.S. Treasury Secretary Steven Mnuchin and senior ministers from France, Britain and the Netherlands have abandoned plans to attend an Oct. 23-25 investor conference in Riyadh.

On Friday, the CEOs of Deutsche Bank and ABB , plus Airbus' defense chief and energy historian Daniel Yergin, joined a list of Western business executives who have withdrawn.

Pakistan's prime minister and a delegation led by Russian Direct Investment Fund head Kirill Dmitriev plan to participate. Britain's BAE Systems is sending senior representatives.

A conference spokesperson confirmed the conference would proceed with an updated program that includes heads of state from the Arab world, Africa and Asia.