Saudi Arabia's Crown Prince Mohammed bin Salman and his close senior officials should be investigated due to considerable evidence they were liable for the alleged assassination of investigative journalist Jamal Khashoggi in the country's Istanbul consulate last year, a United Nations report said Wednesday.

The 100-page report, the result of a six-month investigation led by UN special rapporteur on extrajudicial killings, Agnes Callamard, said Khashoggi's murder on Oct. 2018 had been "planned and perpetrated" by officials of the State of Saudi Arabia.

"It is the conclusion of the Special Rapporteur that Mr. Khashoggi has been the victim of a deliberate, premeditated execution, an extrajudicial killing for which the state of Saudi Arabia is responsible under international human rights law," the report said.

"The Special Rapporteur addresses the question of credible evidence warranting further investigation of high-level officials currently not being criminally charged, specifically Saud Alqahtani, and the Crown Prince Mohammed bin Salman," it added.

The report said evidence suggested the 15-man mission allegedly sent to kill Khashoggi would have required government coordination and it was unlikely that the crown prince would have been unaware of at least some sort of mission being conducted in Istanbul.

Callamard said evidence also suggested that, following Khashoggi's death, the Saudi authorities likely permitted "if not directed" an operation to destroy Khashoggi's remains.

She also decried the lack of transparency in Saudi Arabia's efforts to punish those it says were involved in the journalist's brutal demise.

Initially, the Sunni kingdom arrested 21 people with alleged links to the crime and currently 11 were on trial behind closed doors, five of them facing the death penalty.

The crown prince has denied any knowledge of the killing.

Callamard said Riyadh would be "gravely mistaken" to think that closed-door trials would satisfy the international community.

In the report, which next week is due to be officially presented before the Human Rights Council, the UN special rapporteur on extrajudicial killings urged the international community to sanction Prince Mohammed and his properties until he can prove he was not involved in the assassination.

The Saudi foreign minister, Adel al-Jubeir, refuted the report with a string of statements on his official Twitter page, saying the report contained contradictions and baseless allegations.

He said Saudi Arabia would stand by its right to try the suspects in the country rather than abroad.

Saudi agents allegedly assassinated former Washington Post columnist and Saudi dissident Khashoggi in his country's consulate in Turkey's largest city, Istanbul, where he had gone to file marriage papers that would have allowed him to marry his fiancée Hatice Cengiz, who was waiting outside the building.

The event sparked considerable international outrage directed toward Riyadh.

In the report, Callamard said that Turkey's efforts to conduct an independent investigation into the killing had been undermined by Saudi Arabia and that officials had not been granted sufficient access to the crime scene.

Prince Mohammed, 33, is the apparent heir to the Saudi throne and wields considerable power in the oil-rich nation.

Human rights observers consider the kingdom to have one of the worst records for basic human rights violations. EFE-EPA