SAUDI Arabia has promised a “full” investigation into the killing of journalist Jamal Khashoggi, US Defence Secretary Jim Mattis said following talks with Saudi Foreign Minister Adel al-Jubeir in Bahrain.

“We discussed it … the need of transparency, full and complete investigation. Full agreement from FM Jubeir, no reservations at all,” Mr Mattis told reporters following the talks, during which he warned the Saudi kingdom that the murder attributed to the Saudi authorities risked destabilising the region.

“No reservations at all. He [Jubeir] said we need to know what happened and it was very collaborative, in agreement,” the Pentagon chief told reporters on a flight from Manama to Prague where he will mark the centenary of Czechoslovakia.

Speaking later on at a joint press conference in Prague with Czech Prime Minister Andrej Babis, Mr Mattis gave a nod to Turkey’s probe into the murder.

“Certainly Turkey with the evidence that they have compiled will ensure that there is more than one review of what is going on there and I am certain the investigation will include the evidence that Turkey has put forward so far,” Mr Mattis said.

Saudi journalist Khashoggi, 59, who had criticised the kingdom’s powerful Crown Prince Mohammed bin Salman, had lived in self-imposed exile in the United States since 2017.

He was murdered after entering his country’s Istanbul consulate on October 2 to obtain paperwork to marry his Turkish fiancee.

Gruesome reports have alleged that The Washington Post columnist was killed and dismembered by a team sent from Saudi Arabia to silence him.

After weeks of denials, Riyadh has sought to draw a line under the crisis with an investigation.

Prince Mohammed, heir to the oil-rich nation’s throne, publicly denounced the murder as “repulsive”, while the Saudi prosecutor acknowledged for the first time this week that based on the evidence of a Turkish investigation the killing had been “premeditated”.

But Riyadh over the weekend dismissed Ankara’s calls to extradite 18 Saudis being held over Khashoggi’s murder, as Washington warned the crisis risked destabilising the Middle East.

Addressing a forum in Manama on Saturday, Mr Mattis warned that “the murder of Jamal Khashoggi in a diplomatic facility must concern us all greatly”.

“Failure of any nation to adhere to international norms and the rule of law undermines regional stability at a time when it is needed most,” he stressed.

The murder, which has tarnished the image of Crown Prince Mohammed, has sparked a wave of international criticism and affected Washington’s relations with the kingdom.

The United States relies heavily on Saudi Arabia to counter Iran’s influence in the region and to defend the security of Israel.

Mr Mattis did not have a formal bilateral meeting with Jubeir on the sidelines of the Manama forum, where he met with several Arab and European leaders.

The two men spoke at a dinner gathering all the ministers.