The eldest son of the murdered Saudi journalist, Jamal Khashoggi, has arrived in the US from Saudi Arabia, with family members.

Salah Khashoggi had previously been unable to leave Saudi Arabia due to his father's criticism of the leadership.

He was pictured on Tuesday receiving condolences from de facto Saudi leader Crown Prince Mohammed bin Salman.

Jamal Khashoggi was murdered in the Saudi consulate in Istanbul three weeks ago.

Saudi Arabia's public prosecutor said on Thursday that the killing was premeditated. Saudi officials have also been blaming "rogue" agents as Riyadh has struggled to provide a credible explanation for how Jamal Khashoggi met his end.

At first Saudi Arabia maintained the journalist, who had US residency and contributed to the Washington Post, had left the building "unharmed" on 2 October - then that he had been killed in a brawl.

Turkish investigators, speaking off the record, have said the crown prince must have known what was going on. Riyadh denies he had a role in the death.

Salah Khashoggi briefly shook hands with Crown Prince Mohammed and gave what many see as a cold stare during Tuesday's apparently staged meeting.

Some are suggesting the meeting may have been the price for being allowed to leave the country.

A US spokesman said that Secretary of State Mike Pompeo had told Saudi leaders that he wanted Salah Khashoggi, a dual citizen, to be able to return to the US and was "pleased" that he had been allowed to do so.