UN experts have called for Navalny's urgent medical evacuation from Russia.
A group of UN rights experts expressed alarm Wednesday at the deteriorating health of imprisoned Kremlin critic Alexei Navalny and called for his urgent medical evacuation from Russia.
"We believe Mr Navalny's life is in serious danger," warned the four independent experts on the issues of freedom of expression, torture, extrajudicial executions and the right to physical and mental health.
They called on Russian authorities to allow Navalny "to be evacuated for urgent medical treatment abroad," stressing that "the Russian government is accountable for Mr Navalny's life and health while he is in detention."
Navalny, who is on hunger strike in a Russian penal colony, has been incarcerated under harsh conditions without adequate medical care and has been barred from seeing doctors of his own choosing, they said.
"We are deeply troubled that Mr Navalny is being kept in conditions that could amount to torture or cruel, inhuman or degrading treatment or punishment," said the experts, who are appointed by the UN but do not speak on behalf of the world body.
Their comments came as protests gathered for a series of nationwide demonstrations in support of Navalny, with police moving quickly to make arrests, including of key aides of the jailed opposition figure.
Navalny was detained when he returned to Russia in January after months recovering in Germany from a near-fatal nerve agent poisoning he blames on the Kremlin -- an accusation it rejects.
He was sentenced to two-and-a-half years on old fraud charges his supporters say were politically motivated and has been serving time in a penal colony in the town of Pokrov about 100 kilometres (60 miles) east of Moscow.
His health has been failing since he launched a hunger strike three weeks ago.
"We are extremely concerned that the current danger to Mr Navalny's life, his most recent incarceration and the past attacks on him, including an attempt against his life last August with the nerve agent Novichok... are all part of a deliberate pattern of retaliation against him for his criticism of the Russian government and a gross violation of his human rights," the UN experts said.
Pointing to previous rulings by the European Court of Human Rights, the experts stressed that "there is no valid legal basis for Mr Navalny's arrest, trial and imprisonment in Pokrov."