Navalny, a fearless politician and one of the few figures to pose a real political threat to Russian President Vladimir Putin, died in IK-3 special regime corrective colony in Kharp, in the Yamalo-Nenets Autonomous Okrug in Russia's far northern Arctic region.

The two laboratories tested samples from Navalny that had been smuggled out of the country and had concluded he had been poisoned, his wife said in a video statement. She had been unable to obtain their final reports detailing what kind of poison had been used and called on them to release their findings.

"We all deserve to know this truth. I demand that the results of the research — showing precisely what substance my husband, Alexei Navalny, was poisoned with — be made public. I demand this for myself, for our children, for Alexei's parents, for our supporters in Russia, and for all people everywhere who are fighting for freedom and justice," she said in a statement on Instagram.