Human Rights Watch on Thursday urged allies of Saudi Arabia to review their ties with its Crown Prince Mohammed bin Salman over the disappearance of prominent Saudi journalist Jamal Khashoggi.
"If Saudi Arabia is responsible for Khashoggi's disappearance and possible murder, the United States, United Kingdom, European Union and other Saudi allies need to fundamentally reconsider their relationship with a leadership whose behaviour resembles that of a rogue regime," the New York-based rights group said.
"There is a mountain of evidence implicating Saudi Arabia in the enforced disappearance and potential murder of Jamal Khashoggi," said Sarah Leah Whitson, the group's Middle East director.
"As the days go by, Saudi Arabia's fact-free denials are becoming indictments in and of themselves."
Khashoggi, a critic of the crown prince who is the kingdom's de facto ruler, vanished on October 2 after entering the Saudi consulate in Istanbul.
Turkish police say Khashoggi, a Washington Post contributor who had been in self-imposed exile in the United States, was murdered inside the consulate by a 15-member Saudi team flown into the country, according to Turkish government sources.
Saudi Arabia insists Khashoggi exited the consulate after a brief visit and has repeatedly denied the accusations.
But Whitson said that "given that Saudi Arabia will not provide any evidence about Khashoggi's movements in and out of the consulate, they cannot be trusted to conduct a genuine –- far less effective -– investigation."
In London, Britain's foreign secretary warned Thursday that Saudi Arabia would face "serious consequences" if suspicions of Khashoggi's murder turned out to be true.
"People who have long thought of themselves as Saudi's friends are saying this is a very, very serious matter," Jeremy Hunt told AFP.
"If these allegations are true, there will be serious consequences because our friendships and our partnerships are based on shared values," he said.
HRW also charged that Saudi authorities had "escalated repression against dissidents and critics" since the crown prince was appointed in June 2017.
The watchdog accused the Saudi-led coalition fighting in Yemen of "numerous violations of international humanitarian law, including likely war crimes".
"UN Security Council members should impose targeted sanctions on Mohammad bin Salman and other senior coalition commanders substantially responsible for widespread violations of the laws of war who have not taken serious steps to end abuses," it said.