Alexei Navalny pictured walking down stairs during recovery from novichok poisoning

Russian opposition politician Alexei Navalny has published a photograph of himself walking down stairs in the latest update on his recovery after he was poisoned with a nerve agent in August.

In the post, Mr Navalny said the road to making a full recovery was “clear, although long”. He said he still was not able to use his phone or pour water into a glass, and has problems going up or down steps because his legs tremble.

“There are many problems yet to be solved, but amazing doctors from the Charite hospital have solved the main one,” the post said.

“They turned me from a ‘technically alive human being’ into someone who has high chances to become ... a man who can quickly scroll Instagram and understand without thinking where to put his likes.”

He is being treated in the German hospital after he collapsed during a domestic flight in Siberia and was later airlifted to Berlin.

Germany has said laboratory tests in three countries have determined that Mr Navalny was poisoned with the novichok nerve agent.

On Thursday, members of Mr Navalny’s team said traces of novichok had been found on a water bottle in the Tomsk hotel room where he had been staying before the flight on which he fell ill.

It had previously been suggested that he had been poisoned with a cup of tea he drank in the airport.

According to an Instagram post on Thursday, some of Mr Navalny’s team had remained in Tomsk, and after they heard he had become unwell, made a search of the hotel room.

A video showing the search showed two empty plastic water bottles on a table. The post states: “Two weeks later, a German laboratory found traces of novichok precisely on the bottle of water from the Tomsk hotel room.”

“There was no particular hope of finding anything,” the post said. “But since it was absolutely clear to us that Navalny was not ‘slightly ill’, not ‘overheated’ …  it was decided to take everything that could be hypothetically useful in some way and hand it over to doctors in Germany. The fact that the case would not be investigated in Russia was also quite obvious. And so it happened: almost a month passed, Russia did not recognise Alexei's poisoning.”

Two separate, independent laboratories in France and Sweden confirmed the earlier German finding that Mr Navalny was poisoned with novichok – the same nerve agent used in the Salisbury attack on former Russian spy Sergei Skripal and his daughter in 2018.

The German chancellor, Angela Merkel, said the tests carried out in Germany earlier this month showed “unequivocally” that novichok was used to poison Mr Navalny.

She said the use of the chemical weapon showed that the “dangerous” attack on the long-standing critic of Vladimir Putin was an attempted murder and the aim was to silence him.

She said there remained “very serious questions that only the Russian government can answer and must answer”.

Western governments have demanded an explanation from Russia.

Last week, Mr Navalny’s team said the politician was already planning to return to Russia.

Asked whether the Russian government would consider a meeting between Mr Navalny and Mr Putin after the opposition leader recovers, Kremlin spokesperson Dmitry Peskov, said, according to the Interfax new agency: “We do not see the need for such a meeting, so I believe that such a meeting will not take place.”

Additional reporting by Reuters