Saudi Arabia's foreign minister on Saturday said 18 people arrested over the killing of dissident writer Jamal Khashoggi will be prosecuted in the kingdom, while Turkey says it will seek the extradition of the suspects for a trial on its soil.

"On the issue of extradition, the individuals are Saudi nationals. They're detained in Saudi Arabia, and the investigation is in Saudi Arabia, and they will be prosecuted in Saudi Arabia," Adel al-Jubeir told a regional security conference in the Bahraini capital Manama.

However, authorities in Turkey - where Khashoggi was killed earlier this month - have announced that they will officially demand the extradition of the 18 suspects from Saudi Arabia.

In a statement late Friday, the Turkish justice ministry said Istanbul prosecutors have prepared a requisition for the suspects on charges of planned and deliberate murder with monstrosity and torture.

"We expect that this request for return is met [by Saudi Arabia]. Because this heinous incident took place in Turkey, in Istanbul. Turkish authorities are capable of and determined to shed light on this incident," Justice Minister Abdulhamit Gul was quoted by official Anadolu Agency as saying.

Khashoggi, a Washington Post columnist and critic of Saudi Arabia's powerful Crown Prince Mohammed bin Salman, has not been seen since he walked into the Saudi consulate in Istanbul on October 2.

After weeks of denying knowledge of foul play, the Saudis last week acknowledged that Khashoggi died in the consulate, and the kingdom's chief prosecutor said on Thursday that the murder had been premeditated.

Saudi Arabia has sacked a number of senior officials in connection with Khashoggi's case, including two from Prince Mohammed's inner circle.

In his speech at the Manama conference on Saturday, Foreign Minister al-Jubeir criticized the media's "hysteria" over the murder of Khashoggi.

"Unfortunately, there has been this hysteria in the media about Saudi Arabia being guilty before the investigation is complete," he said.

Al-Jubeir vowed that those responsible would be prosecuted: "We have made it very clear that we are going to have a full and transparent investigation, and the results will be released."

The top Saudi diplomat also promised that mechanisms will be put in place to ensure that such an incident does not happen again.

He called on people to wait until the investigation is completed before judging its results. "Investigations take time," he said.

"Every day we discover new things. Every day we uncover new items and new evidence comes to light," he added.

On relations with the United States, which have been strained by the Khashoggi scandal, al-Jubeir said that the Saudi kingdom has strategic ties with Washington that go back to the 1930s and made clear that "this is not going to change."

US Defence Secretary Jim Mattis also attended the forum and voiced his concerns over the killing of Khashoggi.

"With our collective interests in peace and unwavering respect for human rights in mind, the murder of Jamal Khashoggi in a diplomatic facility must concern us all greatly," Mattis told the conference.

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