United Nations human rights experts have called for an international inquiry into the poisoning of Kremlin critic Alexei Navalny and said that the evidence thus far points to the "very likely involvement" of Russian government officials.
His poisoning was part of a trend of unlawful killings and attempted killings of critics at home and abroad meant to send a "sinister warning" to quash dissent, said Agnes Callamard, UN special rapporteur on summary killings, and Irene Khan, UN expert on freedom of opinion and expression.
Navalny, 44, fell ill in Siberia last August and was flown to Germany, which says it found evidence he had been poisoned with Novichok, a banned nerve agent.
Russian officials deny any role in his illness and say they have not seen proof that he was poisoned.
After recuperating for five months in Germany, Navalny returned to Russia in January.
He was arrested on arrival and sentenced to two and a half years prison for parole violations.
"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," the UN experts said in a statement.
Callamard and Khan also released the text of a December 30 letter to Russian authorities, notifying officials in Moscow they were looking into the poisoning.
The letter said that if allegations were confirmed, Russian officials may be subject to criminal liability "both for participating in or ordering attempted murder or for failing to ensure that subordinates do not engage in these actions".
Australian Associated Press