A Saudi crown prince who President Joe Biden previously said was responsible for the gruesome murder of journalist Jamal Khashoggi has legal protection, the US has ruled.

The Biden administration determined that Prince Mohammed bin Salman has immunity from a lawsuit filed against him over the 2018 killing, the US Department of Justice says.

Khashoggi was dismembered by Saudi agents in the Saudi consulate in Istanbul in an operation which US intelligence believed was ordered by Prince Mohammed, who has been the kingdom’s de facto ruler for several years.

“Jamal died again today,” Khashoggi’s former fiancée, Hatice Cengiz, said on Twitter minutes after the news became public.

She added later: “We thought maybe there would be a light to justice from #USA But again, money came first. This is a world that Jamal doesn’t know about and me..!”

Tweet from @mercan_resifi

Mr Biden was criticised for fist-bumping the crown prince on a visit to Saudi Arabia in July to discuss energy and security issues.

The White House said Mr Biden had told Prince Mohammed that he considered him responsible for Khashoggi’s killing.

The prince has denied ordering Khashoggi’s killing but acknowledged later that it took place “under my watch.”

Sarah Lee Whitson, a spokeswoman for Democracy for the Arab World Now, in a written statement accused Mr Biden of letting the prince off.

“It’s beyond ironic that President Biden has single-handedly assured MBS can escape accountability when it was President Biden who promised the American people he would do everything to hold him accountable,” she said.

“Not even the Trump administration did this.”

In a document filed in US District Court for the District of Columbia, Justice Department lawyers wrote that “the doctrine of head of state immunity is well established in customary international law.”

Justice Department lawyers said that the executive branch of US government, referring to the Biden Administration, had “determined that defendant bin Salman, as the sitting head of a foreign government, enjoys head of state immunity from the jurisdiction of US courts as a result of that office.”

Khashoggi had criticised the crown prince’s policies in Washington Post columns. He had travelled to the Saudi consulate in Istanbul to obtain papers he needed to marry Cengiz, a Turkish citizen.

A spokesperson for the Saudi consulate in Washington could not be reached for comment on Thursday evening after business hours.

“This is a legal determination made by the State Department under longstanding and well-established principles of customary international law,” a spokesperson for the White House National Security Council said in a written statement.

“It has nothing to do with the merits of the case.”

The spokesperson referred further questions to the State and Justice Departments.