The deputy head doctor says the opposition politician's full diagnosis is available, but he cannot disclose it yet.

The deputy head doctor of a hospital in Siberia has said doctors had found no traces of poison in tests carried out on Kremlin critic Alexei Navalny, who became ill while flying back to Moscow from Siberia.

In a briefing on Friday, the doctor, Anatoly Kalinichenko, said the hospital already had a full diagnosis of Navalny's condition, but he could not disclose it yet.

A doctor of the Siberian hospital has said that they have found no traces of poison in tests carried out on Kremlin critic Alexei Navalnyhttps://t.co/6BbsDZl26U

— WION (@WIONews) August 21, 2020

"So far, no poison has been identified in the blood and urine, there is no trace of its presence," he said.

The announcement came shortly after allies of Navalny accused the Kremlin of thwarting his medical evacuation to Germany, saying the decision places his life in mortal danger because the Siberian hospital treating him is under-equipped.

Navalny, a fierce critic of President Vladimir Putin and his lieutenants, is in a serious condition after drinking tea on a plane on Thursday that his allies believe was laced with poison. A doctor on Friday said his condition had improved a little overnight.

Navalny's wife Yulia and his spokeswoman Kira Yarmysh spoke out against the Kremlin after the head doctor at the hospital in Siberia treating Navalny said moving him would put his life at risk because he was still in a coma and his condition unstable.

"The ban on transporting Navalny is an attempt on his life being carried out right now by doctors and the deceitful authorities that have authorised it," Yarmysh wrote on social media.

She said doctors had previously consented to his being moved, but had withheld their agreement at the last minute.

"This decision, of course, was not made by them but by the Kremlin," said Yarmysh.

'Speedy recovery'

The Kremlin said on Thursday medical authorities would promptly consider any request to move him to a European clinic and were being open about his medical condition.

The dispute over moving Navalny broke out as a German air ambulance landed in Omsk, the city where he is being treated, with the intention of flying him to Germany for treatment if possible.

Alexander Murakhovsky, the hospital's head doctor, told reporters many legal questions would need to be resolved before Navalny could be handed over to European doctors.

He said top doctors had been flown in from Moscow to treat Navalny. The Moscow doctors were no worse than their European counterparts, he said.

Dangerous substance

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 who should therefore wear protective suits.

Navalny's team said it believed authorities wanted to stall for time so that any trace of what poisoned him would disappear.

Navalny, a 44-year-old lawyer and anti-corruption campaigner, is among Putin's fiercest critics. He lost consciousness while on a flight on Thursday and his plane made an emergency landing.

Doctors said they were working to save his life after he went into a coma and was put on a ventilator in intensive care.