Saudi Crown Prince Mohammed bin Salman told a top aide in 2017 that he would use “a bullet” on self-exiled journalist Jamal Khashoggi if he did not return to the kingdom and stop criticising the Saudi government, The New York Times reported on Thursday, quoting unidentified officials with access to US intelligence reports.

Khashoggi was killed in the Saudi consulate in Istanbul in October. The conversation, intercepted by American intelligence agencies, is the most detailed evidence to date that Salman considered killing Khashoggi long before a team of Saudi hitmen strangled him and dismembered his body.

Saudi Arabia has repeatedly denied Salman’s involvement in the murder, and in December condemned a US Senate resolution accusing him of ordering the killing of the journalist. They have blamed the murder on a group of rogue Saudi officials. The crown prince is the next in line to the Saudi throne behind his ailing father King Salman, and has become the de facto ruler of Saudi Arabia.

The conversation between Salman and the aide Turki Aldakhil took place in September 2017, when the kingdom’s government was increasingly alarmed about Khashoggi’s criticisms. The same month, Khashoggi started writing opinion columns for The Washington Post, and top Saudi officials discussed ways to lure him back to Saudi Arabia, the intercepted communications show.

Meanwhile, a UN rapporteur investigating Khashoggi’s murder said the killing was planned and carried out by Saudi officials, who exploited diplomatic immunity. In a preliminary report, Agnes Callamard, a UN special rapporteur on extrajudicial killings, said the journalist was the victim of a “brutal, premeditated killing planned and perpetrated by officials of the state of Saudi Arabia”.

Callamard, a French human rights expert, said she had heard “parts of the chilling and gruesome audio material obtained and retained by the Turkish intelligence agency” and claimed that Turkey’s efforts to carry out a proper investigation had “been seriously curtailed and undermined by Saudi Arabia”.

“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,” she added. Callamard is scheduled to deliver the final report to the UN human rights council in June.