The United Nations human rights chief has called on Russia to conduct or cooperate with a "thorough, transparent, independent and impartial investigation" into the alleged nerve agent attack on Russian opposition leader Alexei Navalny.
Michelle Bachelet stressed the need to get to the bottom of the alleged poisoning, after German specialists said they had "unequivocal proof" that the weapons-grade nerve agent Novichok was used in the attack.
"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," she said in a statement.
Mr Navalny, an anti-corruption campaigner and one of President Vladimir Putin's fiercest critics, fell ill on a domestic flight last month and was treated in a Siberian hospital before being evacuated to Berlin.
Michelle Bachelet, United Nation's commissioner for human rights. Source: AAP
The alleged attack marked the latest in a long line of assassination attempts against Mr Putin's critics.
Ms Bachelet stressed on Tuesday that "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".
"And the failure in many cases to hold perpetrators accountable and provide justice for the victims or their families, is also deeply regrettable and hard to explain or justify," she said.
'Numerous questions'
Germany said last week that toxicology tests conducted by its armed forces found "unequivocal evidence" that Mr Navalny had been poisoned with the weapons-grade nerve agent Novichok, the substance used in the 2018 attack on former Russian double agent Sergei Skripal and his daughter in the English city of Salisbury.
The 44-year-old's associates say the use of Novichok, a military-grade nerve agent, shows that only the Russian state could be responsible, but the Kremlin fiercely denies any involvement.
Russia had likewise rejected any link to the Skripal case, as well as the death of former KGB agent Alexander Litvinenko, who was poisoned with highly radioactive polonium-210 at a hotel in the British capital.
While the UN rights office said that they were not in a position to make direct accusations against Russia in the case, Ms Bachelet noted that nerve agents and radioactive isotopes such as Novichok and Polonium-210 were sophisticated substances that are very hard to get hold of.
"This raises numerous questions," she said.
"Why use substances like these? Who is using them? How did they acquire them?"
The UN High Commissioner for Human Rights also pointed out that prior to Mr Navalny's alleged poisoning, he had repeatedly been harassed, arrested and assaulted either by authorities or by unknown assailants.
"Navalny was clearly someone who needed state protection, even if he was a political thorn in the side of the government," she said.
"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."
