US Defence Secretary James Mattis on Saturday condemned the killing of dissident Saudi journalist Jamal Khashoggi as “intolerable” and called it a national security concern for nations in the Middle East.

Such behaviour undermines stability in the Middle East at a time when the region needs it most, said the top US official in Bahrain while speaking at a security conference with top Saudi officials in attendance, including the kingdom’s Foreign Minister.

Mattis reiterated US President Donald Trump’s vow to get to the bottom of what happened to the Washington Post contributor and Saudi government critic, who disappeared after entering the kingdom’s consulate in Turkey on October 2.

Saudi Foreign Minister Adel al-Jubeir criticized the “hysteria” over the issue and said the kingdom was being blamed even before the probe into the case was complete, the Post reported.

Mattis said Secretary of State Mike Pompeo would be taking unspecified “additional measures” in response to the killing beyond the revocation of US visas for certain Saudi suspects.

He characterized the killing as not only a human rights issue but also a national security concern for nations in the Middle East.

“When opposing voices can be heard within a political process adapted to each nation’s culture, one that permits peaceful opposition by giving voice and human rights to all, a nation becomes more secure,” Mattis said.

“When people can speak and be heard calling for peace and respect for all, the terrorist message of hatred and violence is not embraced. With our collective interests in peace and unwavering respect for human rights in mind, the murder of Khashoggi in a diplomatic facility must concern us all greatly.”

Speaking after Mattis, Al-Jubeir said: “This issue has become fairly hysterical. I think people have assigned blame on Saudi Arabia with such certainty before the investigation is complete.

“We have made it clear that we are going to have a full and transparent investigation, the results of which will be released.”

Without calling out Saudi Arabia by name, Mattis suggested Khashoggi’s murder threatened stability in the Middle East at a time when the region can’t afford it.

The region is struggling to cope with conflicts in Syria and Yemen, a political divide between Gulf nations and Qatar.

Besides being the biggest importer of American arms, Saudi Arabia is also a critical partner in the Trump administration’s Middle East agenda, which includes stabilizing Syria, brokering a peace deal between Israel and the Palestinians and bringing an end to the Yemen war.

After weeks of providing conflicting accounts of what happened to Khashoggi, the kingdom last week said that he was killed “accidentally” in a fist fight at the consulate by “rogue” agents.

The kingdom then dismissed five high-ranking officials — including Crown Prince Bin Salman’s media chief and the deputy head of the Saudi intelligence service — and arrested 18 people.

Earlier this week, the Saudi story changed again, with Riyadh’s public prosecutor saying that Khashoggi was killed in a “premeditated” operation.

Mattis said the US’ respect for the Saudi people was undiminished, but added that “with our respect must come transparency and trust”, the report said.