Saudi crown prince told White House slain journalist Jamal Khashoggi was a Muslim extremist

The Saudi crown prince accused of having a hand in the murder of Jamal Khashoggi reportedly told White House representatives the Washington Post journalist was a Muslim extremist.

Crown Prince Mohammed bin Salman made the allegation during a phone call with US President Trump's son-in-law Jared Kushner and another official, the Washington Post reports.

The crown prince stated Khashoggi was a member of the Muslim Brotherhood, prior to Saudi Arabia formally acknowledging it was responsible for the journalist's death.

During the call, Salman stressed the importance of maintaining a US-Saudi Alliance.

READ MORE: Turkey to Saudi: co-operate over Khashoggi

Salman's alleged claims run counter however to public statements later made by the Saudi government, lamenting Khashoggi's death as a "terrible mistake".

"The incident that happened is very painful, for all Saudis,” the crown prince himself said during a panel appearance last week.

“The incident is not justifiable.”

Khashoggi's family have denounced any suggestion the journalist participated in Brotherhood activities.

"Jamal Khashoggi was not a member of the Muslim Brotherhood. He denied such claims repeatedly over the past several years,” the family said.

READ MORE: Saudi Crown Prince Mohammad Bin Salman: Who is the power behind the throne of oil-rich nation?

“Jamal Khashoggi was not a dangerous person in any way possible. To claim otherwise would be ridiculous.”

Turkey's justice minister has meanwhile renewed a call for Saudi Arabia to cooperate in the investigation into the killing, saying "no one can escape responsibility".

Abdulhamit Gul said that Saudi Arabia's top prosecutor – who spent three days in Istanbul as part of joint Turkish-Saudi efforts to investigate the killing – had failed to answer Turkish investigators' questions about the location of the writer's remains as well as who ordered the killing.

"We expect these questions to be answered swiftly," Mr Gul told reporters.

"No one can escape responsibility. This issue has become a world matter.

"It is not an issue that can be covered up."