Doctors removed Russian opposition leader Alexei Navalny from a medically induced coma and say he is “responding to verbal stimuli,” Berlin’s Charité hospital announced Monday.

“The condition of Alexei … has improved. The patient has been removed from his medically induced coma and is being weaned off mechanical ventilation. He is responding to verbal stimuli. It remains too early to gauge the potential long-term effects of his severe poisoning,” Charité hospital said in a statement.

The hospital has been treating Navalny since August 22, when he was airlifted to Germany from Russia after falling ill on a Russian domestic flight from the Siberian city of Tomsk to Moscow. Navalny’s team has accused the Kremlin of poisoning him. The government of President Vladimir Putin has repeatedly denied involvement. German doctors say evidence suggests Navalvy ingested the Soviet-era nerve agent Novichok.

German Chancellor Angela Merkel faces increasing pressure from opposition groups within the country to take a tougher stance over the incident, which Merkel’s government says it has concluded was a Novichok poisoning.

“The incident has put the future of Germany’s ‘Nord Stream 2’ pipeline with Russia in doubt as a growing number of politicians call for support for the project to be withdrawn unless Russia helps to clear up the circumstances around Navalny’s poisoning,” Reuters reported on Monday. The energy project would double the flow of gas from Russia to Europe. On Monday, Merkel’s spokesman said she has not ruled out imposing sanctions on the “Nord Stream 2” pipeline in response to the suspected poisoning.

The Kremlin said on Monday that it was “absurd” to blame Russia for Navalny’s poisoning, according to the BBC.

“Attempts to somehow associate Russia with what happened are unacceptable to us, they are absurd,” Putin’s spokesman, Dmitry Peskov, said. Germany’s assertion that Navalny was poisoned with Novichok “is not backed by evidence,” Russia’s foreign ministry has said, according to the New York Times. 

Before he was airlifted to Germany on August 22, Navalny was first treated at a Siberian hospital in the city of Omsk, where his Moscow-bound flight made an emergency landing on August 20 after he fell ill.

“The chief toxicologist at the Siberian hospital who was the first to treat Navalny, Alexander Sabaev, said he initially suspected poisoning and that he and his colleagues treated him accordingly,” Reuters reported on Sunday.

“Navalny was put on a ventilator and into an induced coma and given the emergency drug atropine,” Sabaev said. This treatment protocol “is in line with usual treatments of Novichok victims,” a medical source allegedly familiar with Navalny’s German test results told Reuters. Atropine is one of the first treatments used to counteract Novichok’s immediate effects, which include slowing heart rate, fluid on the lung, and permanent nerve damage.

Sabaev said he and his fellow doctors changed their minds on the suspected poisoning after Navalny’s test results came back six hours later with no traces of poison in his system.

“As a toxicologist I am sure. There was no Novichok there,” Sabaev said.

Instead of a poisoning, Navalny likely suffered from “a metabolic disorder,” Sabaev said, noting that Navalny’s “blood sugar levels were four times higher than normal and that he had pancreatic problems.” However, Reuters says it interviewed “other Omsk-based medical sources” that dispute Savaev’s “metabolic disorder” diagnosis.