Allies of stricken Kremlin critic Alexei Navalny accused the Russian authorities of thwarting his medical evacuation to Germany on Friday,
saying they're putting his life in danger.
They believe he fell into a coma on Thursday after he drank tea laced with poison, and that the authorities are stalling for time so it can pass out of his system.
The head doctor at the Siberian hospital treating him said Navalny had been diagnosed with a metabolic disease, perhaps caused by low blood sugar.
But he also said traces of industrial chemical substances had been found on Navalny's clothes and fingers, hours after the hospital said doctors did not believe he was poisoned.
Navalny, a fierce critic of Vladimir Putin, fell so ill on Thursday that the plane he was on made an emergency landing.
His team fear the hospital is so under-equipped it puts him at further risk.
Doctors treating him said his condition had improved a little overnight, but he wasn't stable enough to move.
Navalny's spokeswoman Kira Yarmysh said doctors initially agreed to his being moved, but then refused to discharge him at the last minute.
"This decision, of course, was not made by them but by the Kremlin," she wrote on Twitter.
The Kremlin said Friday it was up to doctors to decide whether he was fit to move.
An air ambulance sent by a Berlin-based NGO has landed in Omsk with the intention of taking him to Germany.
Navalny's team cited a police officer as saying a highly dangerous substance had been identified in his body that posed a risk to everyone around him and that they should wear protective suits.
Reuters could not independently confirm that.
Navalny has been the biggest thorn in the Kremlin's side for more than a decade, exposing what he says is high-level corruption. He's been repeatedly detained for mobilizing crowds of young protesters.
There is a long history of Kremlin foes being poisoned or falling ill after suspected poisonings, such as Sergei Skripal, the former double agent poisoned with a nerve agent two years ago in Salisbury, England.
The Kremlin has repeatedly denied involvement in such incidents.