(CNN) There is "sufficient credible evidence" Saudi Arabia's crown prince bears responsibility for the murder of journalist Jamal Khashoggi , and he should be investigated for it, a United Nations special rapporteur said in the first independent investigation into the death.

In a much-anticipated report, released Wednesday, UN investigator Agnes Callamard said that Saudi Arabia was responsible under international law for the "deliberate, premeditated execution" of Khashoggi and current sanctions on some senior officials do not go far enough.

Crown Prince Mohammed bin Salman and his personal assets abroad should be hit by "targeted sanctions," the report recommends, "until and unless evidence is provided and corroborated that he carries no responsibilities for this execution."

A prominent writer and Washington Post columnist, Khashoggi died after entering the Saudi consulate in Istanbul in October 2018. While Riyadh initially denied any knowledge of the incident, Saudi officials later claimed that a group of rogue operators, many of whom belong to Saudi crown prince's inner circle, were responsible for the journalist's death

The Saudi attorney general later acknowledged that Khashoggi was killed in a premeditated murder.

CNN has reached out to the Saudi government for a response to Wednesday's report.

The special rapporteur does not make any conclusions on the guilt of the Saudi crown prince and King. Instead, Callamard says that there is "credible evidence meriting further investigation by a proper authority" as to whether the "threshold of criminal responsibility has been met."

She goes on to say that Khashoggi was "fully aware of the powers held by the Crown Prince" and had expressed fears about what would happen to him if he returned to the kingdom.

Callamard also says that current international sanctions against some senior Saudi officials do not go far enough, failing to address the top of the kingdom's "chain of command."

These sanctions "fail to correspond to the gravity of the crime or to the fact that the State of Saudi Arabia is ultimately responsible for the violation of Mr. Khashoggi's right to life," she added.

Indeed Germany is the only Western government to suspend future arms sales to Saudi Arabia, the world's largest arms importer, the report said.

Riyadh has maintained that neither bin Salman nor King Salman knew of the operation to target Khashoggi. US officials, however, have said such a mission -- including 15 men sent from Riyadh -- could not have been carried out without the authorization of bin Salman.

Gruesome recording

According to the report -- which cites evidence from Turkish and other intelligence agencies -- after entering the consulate, Khashoggi was injected with a sedative and then his head put inside a plastic bag and suffocated.

It quotes an audio recording from inside the consulate, in which Khashoggi is heard being told he will be taken to Saudi Arabia.

"We will have to take you back. There is an order from Interpol," a Saudi man tells the journalist, who replies that "there isn't a case against me" and warns them that people are waiting for him outside the consulate.

The men instruct Khashoggi to write a text message to his son, and argue over what he should say before a voice says, "cut it short."

"There is a towel here. Are you going to give me drugs?" Khashoggi asks.

"We will anesthetize you," a man responds.

A struggle can then be heard, after which a man asks whether Khashoggi has passed out.

"He raises his head."

"Keep pushing."

"Push here; don't remove your hand; push it."

It has previously been reported that after Khashoggi was killed, his body was dismembered and removed from the consulate in separate bags. It has not been found.

The special rapporteur found credible evidence pointing to the crime scenes having been "thoroughly, even forensically, cleaned" -- indicating that the Saudi investigation was "not conducted in good faith, and that it may amount to obstructing justice."

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Repercussions for Riyadh

Khashoggi's killing and the continued fallout from it has caused a diplomatic crisis for Riyadh , ruining Saudi Arabia's already shaky international reputation and leading many allies to distance themselves from bin Salman.

While US President Donald Trump has shied away from taking a hard line against bin Salman, wishing to retain Riyadh's support in pressuring Iran and flow of money for arms sales, other American politicians have sought to punish the Saudis.

Weeks after the killing, top US officials called for a ceasefire in the Saudi-led but US-supported war in Yemen, and Congress has voted to end US involvement in that conflict entirely -- though Trump vetoed that motion

Bin Salman's " Davos in the Desert " summit weeks after the Khashoggi killing was a failure after many high profile guests pulled out, and investment in the Kingdom has also suffered since Khashoggi's killing, at a time when the Crown Prince is desperately trying to get foreign backing for his Vision 2030 plan.

Washington has also eased up on Saudi rival Qatar, after initially backing Riyadh's attempts to blockade its fellow Gulf monarchy.