WASHINGTON (AFP) - The United States on Monday (Dec 23) welcomed death sentences issued by Saudi Arabia against five people over the murder of Mr Jamal Khashoggi, as Turkey and the journalist's fiancee slammed the verdicts.

"Today's verdicts were an important step in holding those responsible for this terrible crime accountable," a State Department official told reporters after the ruling, which was lambasted as a travesty by Turkey, rights groups, and The Washington Post, to which Khashoggi contributed.

The court however exonerated two top aides to Saudi Arabia's powerful Crown Prince Mohammed bin Salman, whom the United States Senate considers responsible for Khashoggi's murder in October last year at Riyadh's consulate in Istanbul.

The United States "encouraged Saudi Arabia to undertake a fair and transparent judicial process", the official added. "We're pressing them for more transparency and for holding everybody accountable."

Riyadh has described the murder as a "rogue" operation, but both the CIA and a United Nations special envoy have directly linked Prince Mohammed to the killing, a charge the kingdom vehemently denies.

The government of US President Donald Trump has been careful to not attribute such blame to the prince, giving priority to maintaining good relations with the kingdom which is a major arms buyer and ally against Iran.

But Turkey lashed out on Monday at the court’s "scandalous" verdicts over the 2018 murder, saying those responsible for the murder had been granted immunity.

Turkey fuelled international outrage at the 59-year-old Washington Post contributor’s death by releasing video footage that contradicted Saudi Arabia’s initial denial of involvement.

"Those who dispatched a death squad to Istanbul on a private jet... and sought to sweep this murder under the rug have been granted immunity," President Recep Tayyip Erdogan’s top press aide, Fahrettin Altin, wrote on Twitter.

Turkish officials said at the time a 15-strong group of killers strangled him and cut his body into pieces. His remains were never found.

"To claim that a handful of intelligence operatives committed this murder is to mock the world’s intelligence," Mr Altin wrote. "Turkey will continue its efforts to shed light on this incident."

Mr Khashoggi had gone to the Saudi consulate on Oct 2 last year to obtain paperwork for his wedding to Turkish fiancee Hatice Cengiz.

"I find it unacceptable and far from rules of law," she told AFP, referring to the Saudi sentencing.

The Turkish foreign ministry said the verdict was “far from meeting the expectations of both our country and the international community to shed light on the murder with all its dimensions and deliver justice".

The ministry also said key aspects of the murder, including the whereabouts of Mr Khashoggi’s body, were "left in the dark", which the ministry said was a "fundamental deficiency" in terms of accountability.

"It is not only a legal but also a conscientious responsibility to shed light on this murder committed in our territory and to punish all those responsible," added the ministry.

It reiterated Turkey’s expectation of judicial cooperation from Saudi authorities.

Turkey’s ties with Saudi Arabia came under strain after the brutal murder, which tarnished the international reputation of Prince Mohammed.