Turkey's President Recep Tayyip Erdogan said the order to murder Jamal Khashoggi came from "the highest levels" of the Saudi government as he promised no let-up in the hunt for his killers.

A month on from Khashoggi's murder in the Saudi consulate in Istanbul, Erdogan on Friday said he did "not believe for a second" that King Salman was to blame.

Read more

Khashoggi's body was 'dissolved'

But he pointedly failed to absolve Crown Prince Mohammed bin Salman of responsibility for unleashing a "death squad" against the outspoken Saudi journalist whose death has badly tainted the kingdom's de facto ruler.

And in an editorial for Khashoggi's former employer, The Washington Post, Erdogan accused authorities in Riyadh of refusing to answer key questions about the murder, despite their arrest of 18 suspects a fortnight ago.

Erdogan's comments came shortly after one of his top lieutenants charged that Khashoggi's dismembered body was "dissolved" in the consulate as part of an effort to leave no trace of the killing.

"Over the course of the past month, Turkey has moved heaven and earth to shed light on all aspects of this case. As a result of our efforts, the world has learned that Khashoggi was killed in cold blood by a death squad, and it has been established that his murder was premeditated," Erdogan wrote in The Post.

"We know that the perpetrators are among the 18 suspects detained in Saudi Arabia. We also know that those individuals came to carry out their orders: Kill Khashoggi and leave. Finally, we know that the order to kill Khashoggi came from the highest levels of the Saudi government."

But he said his government would keep asking other questions "the Saudi authorities have refused to answer", such as the whereabouts of Khashoggi's body and who ordered his assassination.

The murder of the royal insider-turned-dissident has provoked widespread outrage and sharp criticism from Washington, usually the staunchest of allies.

While President Donald Trump has ruled out halting arms deal with Riyadh as a punishment, his administration has effectively withdrawn support for the Saudi-led coalition's war in Yemen in a stark illustration of the cooling of ties.

Addressing mourners at a memorial service in Washington on Friday, the murdered journalist's fiancee called on Trump to back Turkey's efforts to investigate his death.

"I would like to send this message to Mr Trump: I would like him to support Turkey's legal efforts in trying to bring light to the situation and to discover the whereabouts of his body," Hatice Cengiz said in a recorded message.

Turkey's chief prosecutor said this week that Khashoggi was strangled as soon as he entered the consulate and also confirmed the body was dismembered.

Yasin Aktay, an advisor to Erdogan, hinted in an article published on Friday that the body may even have been destroyed in acid.

"We now see that it wasn't just cut up, they got rid of the body by dissolving it," an official in Turkey's ruling party, he told the Hurriyet newspaper.

"According to the latest information we have, the reason they cut up the body is it was easier to dissolve it."

A Turkish official has previously told The Post that "biological evidence" found in the consulate garden indicated the body was likely disposed of near the murder scene.

Saudi authorities have denied Turkish police permission to search a well in the garden, but allowed them to take water samples for analysis, according to local reports.

The murder has strained the decades-old alliance between the United States and Saudi Arabia, with Trump calling it "one of the worst cover-ups in history".

After initially insisting Khashoggi left the consulate unharmed, then saying he died in a brawl during an interview gone wrong, the Saudi regime admitted he was killed, blaming a "rogue operation".

The crown prince has denounced the murder as "repulsive" and denied any involvement.