A UN court slammed Turkey on Monday for failing to free one of its judges rounded up in Ankara's post-coup crackdown and said it would report the country to the Security Council.
"The government of Turkey has failed to comply with its obligations" in the case of detained judge Aydin Sefa Akay, the court ruled.
"This matter shall be reported to the UN Security Council," presiding judge Theodor Meron added in his ruling.
Akay was one of more than 40,000 people arrested in the aftermath of the failed July putsch against Turkish President Recep Tayipp Erdogan.
The UN court ordered in late January that Akay should be released by mid-February so he can return to his work in The Hague, where the appeals case of a former Rwandan minister has been paralysed by the judge's absence.
Defence lawyers for Rwandan Augustin Ngirabatware had called on the tribunal to report Turkey to the UN Security Council for non-compliance with the court's order.
Ankara has snubbed repeated requests by the UN's Mechanism for International Criminal Tribunals (MICT), which is hearing the case, to explain its actions.
Meron has insisted that Akay, a former diplomat who was nominated to the bench by Ankara, has diplomatic immunity and has repeatedly voiced concern over the conditions of his detention.
"Because Turkey refuses to release Judge Akay, Dr Ngirabatware's case is at a standstill," defence lawyer Peter Robinson wrote in his February motion.
"He remains in prison for a crime he did not commit, waiting for a hearing he cannot have."