- UN human rights experts say the truth must be found about the "sinister positioning" of Kremlin critic Alexei Navalny.
- The experts have also demanded Navalny's release from a Russian penal colony.
- Navalny was poisoned last August with the lethal nerve agent Novichok planted in his underpants.
UN human rights experts called Monday for an international investigation into the poisoning of Kremlin critic Alexei Navalny, as the EU agreed to sanction top Russian officials involved in his detention.
Agnes Callamard, the UN's special rapporteur on extrajudicial, summary and arbitrary executions, and Irene Khan, the top expert on freedom of opinion and expression, stressed the importance of finding the truth about the "sinister poisoning" and ensuring accountability.
They also demanded Navalny's "immediate release" from a Russian penal colony, where he was transferred last week from a Moscow prison.
President Vladimir Putin's most prominent opponent has been sentenced to two-and-a-half years in a penal colony for violating parole terms while in Germany recovering from a poisoning attack.
The 44-year-old spent months recuperating from the near fatal poisoning with the Soviet-era nerve agent Novichok that he claims was ordered by Putin - a claim the Kremlin has repeatedly denied.
EU member states approved sanctions on four senior Russian justice and law enforcement officials involved in his detention, who will be banned from travelling to the bloc and see any assets they hold there frozen.
- 'Clear, sinister warning' -
The UN experts meanwhile warned that Navalny's poisoning with Novichok may have been "deliberately carried out to send a clear, sinister warning that this would be the fate of anyone who would criticise and oppose the government.
"Novichok was precisely chosen to cause fear," said the independent experts, who are appointed by the UN but do not speak on its behalf.
They published a letter they sent to Russian authorities last December, in which they had detailed evidence pointing to "the very likely involvement of government officials in the poisoning, presumably at high level."
The letter was made public after the expiry of a 60-day confidentiality clause, the experts said, adding that the Kremlin had yet to respond.
They pointed out that the novel form of Novichok used in the poisoning "could only be found within and amongst state actors."
The letter also pointed out that at the time of the poisoning, Navalny had been under "intensive government surveillance... making it unlikely that any third party could have administered such a banned chemical without the knowledge of the Russian authorities."
The attack against Navalny, they said, appeared to fall within a wider trend seen over decades of arbitrary killings and attempted murders of government critics.
The experts said.
This pattern requires an emphatic and persistent response by the international community to protect the fundamental rights to life and freedom of expression at the foundation of international human rights.
- 'Matter of urgency' -
They also pointed to previous attacks on Navalny, including "at least two other poisoning attempts, insisting Russian authorities had at the very least failed in their duty to protect him.
"The government cannot escape its obligations under international human rights law by denying responsibility for the act itself," the experts said.
"Even in the unlikely event that a third party could somehow have committed this act, Russia would have failed in its obligation to protect the life of Mr. Navalny against such non-state actors."
They deplored that to date, the authorities had shown no signs of seriously investigating his poisoning, saying the lack of action stood in "stark contrast" to their immediate move to arrest him upon his return to Russia in January.
"Given the inadequate response of the domestic authorities, the use of prohibited chemical weapons, and the apparent pattern of attempted targeted killings, we believe that an international investigation should be carried out as a matter of urgency in order to establish the facts and clarify all the circumstances concerning Mr. Navalny's poisoning," they insisted.
The experts also demanded "Navalny's immediate release", and stressed that the Russian government was responsible for his "care and protection" and would "be held responsible for any harm that may befall him."