The top United Nations human rights official called on Russia on Tuesday to conduct, or cooperate with, a full independent investigation into Germany's findings that opposition leader Alexei Navalny was poisoned with a Novichok nerve agent.
Navalny has been removed from a medically induced coma and is responding to speech, Berlin's Charite hospital said on Monday. The hospital has been treating Navalny since he was airlifted to Germany after falling ill on a Russian domestic flight last month.
Moscow says it has seen no evidence he was poisoned.
"It is not good enough to simply deny he was poisoned, and deny the need for a thorough, independent, impartial and transparent investigation into this assassination attempt," Michelle Bachelet, UN High Commissioner for Human Rights, said in a statement.
"It is incumbent on the Russian authorities to fully investigate who was responsible for this crime – a very serious crime that was committed on Russian soil."
German Chancellor Angela Merkel has said her government has concluded that Navalny, 44, was poisoned with Novichok, the same substance that Britain said was used against Russian double agent Sergei Skripal and his daughter, both of whom survived, in an attack in England in 2018.
The number of cases of poisoning, or other forms of targeted assassination, of current or former Russian citizens, either within Russia itself or on foreign soil, over the past two decades is profoundly disturbing," Bachelet said.
Her spokesman, Rupert Colville, cited the Skripal case and the poisoning of Russian defector Alexander Litvinenko, who was killed in London in 2006.
"These are not materials that you can buy in a pharmacy or a farm shop or a hardware store," Colville said of Novichok and Polonium-210, with which Litvinenko was poisoned.
Proper legal processes have not been carried out in previous incidents, resulting in "close to total impunity" in Russia, he said.