PRAGUE: US Defense Secretary Jim Mattis said on Sunday that he had met Saudi Arabia’s foreign minister and called for a transparent investigation into the killing of journalist Jamal Khashoggi.

Mattis said he met Saudi Foreign Minister Adel al-Jubeir during a conference in Bahrain on Saturday and discussed the killing.

“We discussed it. You know the same thing we talked about, the need for transparency, full and complete investigation,” Mattis told a small group of reporters travelling to Prague with him.

“(There was) full agreement from foreign minister Jubeir, no reservations at all, he said we need to know what happened and it was very collaborative, in agreement,” Mattis added.

Washington Post columnist Khashoggi’s murder has escalated into a crisis for the world’s top oil exporter as Saudi Arabia's allies have reacted with outrage.