Amnesty International said on Saturday that Saudi Arabia's explanation of journalist Jamal Khashoggi's death in the Saudi consulate in Istanbul appeared to be a whitewash of "an appalling assassination.""The investigation findings by the Saudi authorities claiming that Khashoggi died as a result of a 'fist-fight' inside the consulate are not trustworthy and marks an abysmal new low to Saudi Arabia's human rights record," Samah Hadid, the human rights group's Middle East director, said in a statement. It called on Saudi authorities to produce Khashoggi's body so that independent forensic experts could perform an autopsy. It also said the United Nations should investigate his death."An independent investigation will be the only guarantee against what increasingly appears as a Saudi whitewash surrounding the circumstances of Khashoggi's murder or any attempts by other governments to sweep the issue under the carpet to preserve lucrative arms deals and other business ties with Riyadh," Hadid said.Saudi Arabia's claim that Khashoggi had died in a fight -- rather than was deliberately killed - was Riyadh's first acknowledgement of his death after two weeks of denials that it was involved in his disappearance."This appalling assassination within the grounds of the Consulate amounts to an extrajudicial execution," Amnesty said.