Saudi Arabia has admitted that dissident journalist state media has reported.
Saudi journalist Khashoggi, a critic of the kingdom's leadership and a Washington Post contributor, was last seen on October 2 entering his country's consulate in Istanbul.
His disappearance had been, with Turkish officials accusing Saudi Arabia of a state-sponsored killing.
"The discussions between Jamal Khashoggi and those he met at the kingdom's consulate in Istanbul... devolved into a fistfight, leading to his death," the Saudi Press Agency said, citing the public prosecutor.
That explanation is contrary to multiple reports of how Khashoggi died.
Turkish officials told The New York Times that it has audio evidence which 
It also contradicts the Saudi government's earlier account of events. Officials previously told reporters the dissident journalist left the consulate shortly after he arrived.
Missing journalist Jamal Khashoggi. Saudi Arabian state television has now confirmed he is dead. Source: AAP
Turkish police are searching a forest on the outskirts of Istanbul and a city near the Sea of Marmara for the remains of Khashoggi more than two weeks after he vanished after entering the Saudi consulate in Istanbul, two senior Turkish officials told Reuters.
Turkish officials have said they believe Khashoggi was murdered at the consulate and his body chopped up and removed. Riyadh strongly denies the allegations and said it is investigating the disappearance of the journalist, who was critical of Saudi rulers, calling for reforms.
A still image from a security cam claims to show Jamal Khashoggi arriving at Saudi Arabias consulate in Istanbul. Source: ABACA
Saudi Arabia also announced that 18 people had been arrested in the ongoing probe.
The Saudi king also ordered the setting up of ministerial committee under the chairmanship of the crown prince to restructure the kingdom's intelligence agency and "define its powers accurately", state media said.
Shortly before Riyadh confirmed that Khashoggi had been killed, Turkey's President Recep Tayyip Erdogan and Saudi King Salman agreed in telephone talks to continue cooperation in the investigation into the Khashoggi affair.
Erdogan and Salman "emphasised the importance of continuing to work together with complete cooperation", said a Turkish presidential source, who asked not to be named.
The United States warned of a "wide range" of responses should it determine that Saudi Arabia is behind the death of the journalist.
But US President Donald Trump said he found Saudi Arabia's assertion that dissident journalist Jamal Khashoggi died as a result of a fight credible.
"I do, I do," he said when asked if the Saudis' explanation was credible, while adding: "It's early, we haven't finished our review or investigation."
On Thursday President Trump said he presumes Khashoggi is dead and that the US response to Saudi Arabia will likely be “very severe” but that he still wanted to get to the bottom of what exactly happened.
“It certainly looks that way to me. It’s very sad,” Mr Trump told reporters before boarding Air Force One on a political trip.
In an interview with the New York Times on Thursday, Mr Trump said based his acknowledgment that Khashoggi was dead on intelligence reports.
Protestors demonstrate at the entrance of Saudi Arabia consulate over the disappearance of Saudi journalist Source: SIPA USA
Mr Trump said he was waiting for the results so that “we can get to the bottom of this very soon” and that he would be making a statement about it at some point.
His top diplomat Mike Pompeo told Voice of America Radio: "We'll certainly consider a wide range of potential responses."
The Trump administration has been notably slow to criticise Saudi Arabia, despite mounting evidence that Khashoggi, a critic of the Islamic petro-state's powerful crown prince, vanished after entering the Saudi consulate in Istanbul.
The Khashoggi case has presented Mr Trump with one of the most acute foreign policy crises of his nearly two-year-old presidency.
US Secretary of State Mike Pompeo is greeted by Deputy Governor of Ankara Murat Soylu, in Ankara, Turkey. Source: AP
The controversy has put the kingdom - for decades a key Western ally and bulwark against Iran in the Middle East - under unprecedented pressure to offer an explanation to take the heat off its rulers.
With wires
