Doctors treating Russian opposition figure Alexei Navalny say he is out of an induced coma and his condition, since being poisoned, has improved.
He is responding to verbal stimuli, they said. Mr Navalny, 44, was flown to Germany after falling ill on a flight in Siberia in August.
His team allege he was poisoned on the orders of Russian President Vladimir Putin, who denies any involvement.
German doctors say the Putin critic was poisoned with a Novichok nerve agent.
“He is responding to verbal stimuli. It remains too early to gauge the potential long-term effects of his severe poisoning,” it said.
It also said doctors were in close contact with Mr Navalny’s wife.
Mr Navalny is an anti-corruption campaigner who in recent years has become the most prominent opposition politician in Putin’s Russia.
What happened to Alexei Navalny?
Mr Navalny fell ill on 20 August on a flight from Tomsk to Moscow. His supporters suspect poison was placed in a cup of tea at Tomsk airport.
The plane was diverted to Omsk, where the opposition politician was admitted to an emergency hospital. Russian officials initially refused to allow Mr Navalny to be transferred abroad for medical treatment but after three days he was flown by air ambulance to Berlin.
Last week, doctors in Germany said the results of toxicology tests carried out at a military laboratory gave “unequivocal proof” that Mr Navalny was poisoned with a Novichok nerve agent.
Doctors in Omsk insisted that no poisonous substances had been detected in Mr Navalny’s body when he was under their care.
On Monday, the Kremlin said it was “absurd” to blame Russia for Mr Navalny’s poisoning. “Attempts to somehow associate Russia with what happened are unacceptable to us, they are absurd,” Mr Putin’s spokesman, Dmitry Peskov, said.
Russian foreign ministry spokeswoman Maria Zakharova said the allegation that Novichok was used was not backed up by evidence.
A Novichok nerve agent was used to poison former Russian spy Sergei Skripal and his daughter in the UK in 2018. A UK investigation blamed the Russian state.
What’s the international reaction?
On Monday, the British government summoned the Russian ambassador to the UK “to register deep concern about the poisoning”.
In Germany there is growing pressure for Chancellor Angela Markel to take a tougher stance over the incident. Last week, she said Mr Navalny was the victim of attempted murder and that the world would look to Russia for answers.
Russia faces diplomatic fallout
Analysis by Damien McGuinness, BBC News, Berlin
Alexei Navalny’s condition has improved but the German-Russian relationship looks far less healthy.
German Foreign Minister Heiko Maas says that if Moscow fails to co-operate with investigations into the poisoning within the next few days, Berlin will start talking to European partners about sanctions.
An even more explosive threat is that for the first time Angela Merkel’s government is no longer ruling out halting building work on the nearly completed pipeline Nord Stream 2, which is supposed to bring Russian gas to Germany using a pipeline beneath the Baltic Sea.
But stopping the project would be costly. Around 120 European companies are involved and the total cost is more than €9bn (£8bn; $10.6bn). Germany would have to pay damages.
Chancellor Merkel may be under pressure. But German society is divided on how to deal with the Kremlin and German attitudes towards Russia are varied and complex. So tough anti-Moscow rhetoric is not a vote-winner. If action is needed, Mrs Merkel’s preference will be targeted and co-ordinated action with the rest of the EU.
A spokesman for the German government said on Monday that it was too early to make a decision about Nord Stream. He said that Russia had “serious questions” to answer but that a response could not be expected in “three to four days”.
The project must be completed despite current “difficulties”, said Russian Energy Minister Alexander Novak according to Interfax news agency.
When asked on Monday about the Nord Stream 2 pipeline, Mr Trump re-iterated US opposition to the gas project.
There have been a number of previous attacks on high-profile critics or opponents of President Putin, including politicians, intelligence officers and journalists. The Kremlin has always denied involvement.
What is Navalny known for?
Mr Navalny is an anti-corruption campaigner who has led nationwide protests against the Russian authorities. He first made his mark in 2008 when he started blogging about alleged malpractice and corruption at some of Russia’s big state-controlled corporations.
He has called Mr Putin’s party a place of “crooks and thieves” that is “sucking the blood out of Russia”, and has faced attacks in the past.
However, he has been banned from standing against Mr Putin in recent elections because of a conviction for embezzlement. He denies the crime, saying his legal troubles are Kremlin reprisals for his fierce criticism.