Several rights groups have called on Turkey to urgently ask Secretary General Antonio Guterres to establish a United Nations investigation into possible extrajudicial execution of prominent Saudi journalist Jamal Khashoggi.

Speaking at a press conference hosted by the UN Correspondents Association, The Committee to Protect Journalists, Human Rights Watch, Amnesty International and Reporters Without Borders all called for an international probe to determine the circumstances surrounding Saudi Arabia’s role in the enforced disappearance and possible killing of Khashoggi.

The groups said Turkey should enlist the UN to initiate a timely, credible and transparent investigation, arguing that UN involvement would provide the best guarantee against a Saudi whitewash or attempts by other governments to sweep the issue under the carpet to preserve lucrative business ties with the Kingdom.

Khashoggi entered the Saudi consulate in Istanbul on October 2 and has not been seen or heard from since.

Saudi Arabia has denied involvement in Khashoggi’s disappearance, claiming he left the consulate on his own shortly after his arrival, but it has failed to produce any evidence supporting this claim.

Turkey has initiated a criminal investigation and has conducted a forensic investigation of the consulate where Khashoggi was last seen.

Saudi Arabia is said to be cooperating with the probe but rights groups have questioned the independence and impartiality of such actions given both Turkey and Saudi Arabia’s poor treatments of journalists.