Washington DC - President Donald Trump on Tuesday defended Crown Prince Mohammed bin Salman over the gruesome murder by Saudi agents of US-based journalist Jamal Khashoggi and praised the royal's human rights record.

Khashoggi, a columnist for The Washington Post and a US resident, was "extremely controversial," Trump claimed, while welcoming the Saudi heir to the throne in the White House.

"A lot of people didn't like that gentleman that you're talking about. Whether you like him or didn't like him, things happened, but [the prince] knew nothing about it," Trump told reporters.

Khashoggi was killed in 2018 inside the Saudi consulate in Istanbul, Turkey. The murder and dismemberment of the journalist, who'd been critical of the Saudi rulers, briefly caused a diplomatic crisis and prompted criticism from Trump, who was then serving his first term.

Saudi officials later said his murder was a rogue operation, rather than something ordered by the leadership.

Prince Mohammed said at the White House that the murder was "painful and it's a huge mistake, and we are doing our best that this doesn't happen again."

Trump chided the reporter who asked about the scandal, ordering to "leave it at that."

"You don't have to embarrass our guest by asking a question like that."

Trump (79) opened his remarks in the Oval Office by lauding Prince Mohammed as a "very good friend" and claiming he'd done an "incredible" job on "human rights, and everything else."