An official Saudi Arabian investigation into the murder of journalist Jamal Khashoggi by Saudi agents failed to examine who may have ordered the killing and ignored key suspects, a U.N. special rapporteur said on Wednesday.

Saudi Crown Prince Mohammed bin Salman, a key adviser, and other senior officials should be investigated over the premeditated murder at its consulate in Istanbul, given the evidence against them, said Agnes Callamard, U.N. investigator on extrajudicial executions who undertook her own inquiry.

Saudi officials have long denied suspicions in the CIA and some Western countries that the crown prince, the kingdom's de facto ruler, ordered the killing in October.