ISTANBUL — The U.N. human rights expert leading an independent inquiry into the murder of journalist Jamal Khashoggi said Thursday that Saudi Arabia had “seriously curtailed and undermined” Turkey’s attempts to investigate Khashoggi’s killing in the Saudi Consulate in October.

The expert, Agnes Callamard, released preliminary findings of her team’s inquiry Thursday after a week-long fact-finding mission to Turkey that ended Sunday.

“Evidence collected during my mission to Turkey shows prime facie case that Mr. Khashoggi was the victim of a brutal and premeditated killing, planned and perpetrated by officials of the State of Saudi Arabia,” she said in a statement.

 The comments by Callamard, the United Nations’ special rapporteur on extrajudicial, summary or arbitrary executions, added weight to Turkey’s repeated assertions that Saudi Arabia had thwarted the work of Turkish investigators by limiting their access to Saudi diplomatic facilities and refusing to reveal the location of Khashoggi’s remains.

 “Woefully inadequate time and access was granted to Turkish investigators to conduct a professional and effective crime-scene examination and search required by international standards for investigation,” Callamard said.  

 In the year before his death, Khashoggi had contributed columns to The Washington Post that were sometimes critical of Crown Prince Mohammed bin Salman, Saudi Arabia’s day-to-day ruler. On Oct. 2, after Khashoggi entered the Saudi Consulate in Istanbul to pick up documents that would allow him to remarry, he was killed and dismembered by a team of Saudi agents who were waiting for him inside the mission, according to Turkish and Saudi prosecutors. 

The CIA concluded with medium-to-high confidence that Mohammed ordered Khashoggi’s killing because he was a high-profile critic. Saudi officials have rejected that assertion, saying the team of Saudi agents in Istanbul had disobeyed orders to bring Khashoggi home alive and planned his murder on its own.  

Callamard said she initiated her investigation on her own because the United Nations had been unwilling to pursue an international criminal investigation. Her four-person team has no authority to bring criminal charges and will present the findings of its investigation to the U.N. Human Rights Council in June.   

In Turkey, Callamard’s team met with senior Turkish officials, including Istanbul’s chief prosecutor and the head of Turkish intelligence. The team was “given access to some crucial information about Mr. Khashoggi’s murder, including to parts of the chilling and gruesome audio material obtained and retained by the Turkish Intelligence agency,” Callamard’s statement said.

She did not say what the audio revealed. Western intelligence officials have said that listening devices planted in the Saudi Consulate by Turkish intelligence captured the Saudi operatives discussing plans to subdue and kill Khashoggi, as well as the journalist’s terrible last moments — his gasps for air during a physical struggle, then the sound of what was believed to be the electric saw that was used to dismember his body.   

Callamard’s team was not able to meet with some Turkish investigators who had been working on the case and called on Turkey to “promptly fulfill their pledge to provide access to forensic, scientific and police reports.” Callamard had also sought access to the Saudi Consulate in Istanbul and made a request to visit Saudi Arabia, according to a spokesman. Her statement Thursday did not say whether the Saudi authorities had granted either of those requests.

She has also asked for meetings with U.S. officials, including at the CIA, at the State Department and in Congress. “I intend to continue to consider evidence in the weeks to come and would urge anyone who has knowledge or intelligence about what took place before and after Mr. Khashoggi’s murder to share it with us,” her statement said.