The fiancee of slain Saudi Arabian journalist Jamal Khashoggi has called on the Japanese government to bring up the issue of his murder during the Group of 20 summit in Osaka starting Friday in hopes of getting to the bottom of the high-profile case.

"I want to find out who will claim responsibility for it," 36-year-old Hatice Cengiz said in London on Monday, noting that "many questions" remain over the death of Khashoggi inside the Saudi Consulate in Istanbul last October.

The Washington Post columnist had long been critical of Saudi Arabia's royal family.