The European Court of Human Rights (ECHR) is calling on Russia to release top Kremlin critic Alexey Navalny.
ECHR said in a press release Wednesday that it "grants an interim measure in favor of" Navalny and "asks the Government of Russia to release him."
The court's ruling demanded that Navalny be released immediately, warning that failure to do so would mark a breach of the European human rights convention.
The court pointed to Rule 39 of its regulations, citing "the nature and extent of risk to the applicant's life."
Navalny, 44, has been jailed since his return to Russia last month. Moscow said he violated the terms of his probation while recuperating in Germany from a poisoning attack. The sentence stems from a 2014 embezzlement conviction ECHR has ruled to be unlawful.
Navalny was treated in Germany following a nerve-agent poisoning in Siberia last August. He blamed Russia for the poisoning, a charge denied by the Kremlin.
Several western countries have called for Navalny's release, threatening to impose sanctions against Russia over the case.
The Russian Justice Ministry warned in a statement that the ECHR's demand would represent a "crude interference into the judicial system" of Russia and "cross the red line."
ECHR is the international court of the Council of Europe, Europe's main human rights forum.
In the past, it has complied with ECHR's rulings to compensate Russian citizens who contested verdicts in Russian courts, but it has never faced a demand by the court to release someone who has been detained.