The condition of Russian opposition leader Alexei Navalny, who is the suspected victim of poising, is improving even though he is still in an induced coma, according to the German doctors treating him in Berlin.

44-year-old Navalny, the leader of the so called “non-systemic”, that is non-parliamentary, opposition to Russian President Vladimir Putin, has been treated at the Charité Hospital in the German capital for nearly a week now.

He fell ill on a plane flight back to Moscow during a visit in Siberia, leading to an emergency landing and his original hospitalization in the city of Omsk.

After the initial refusal of the Russian authorities, Navalny was transported for treatment in Berlin after German Chancellor Angela Merkel herself called for his transfer. On Friday, Merkel urged Russia to investigate Navalny’s potential poisoning in “full transparency”.

The German doctors found indications of “cholinesterase inhibitors” in his system. Cholinesterase inhibitors block the breakdown of a key chemical in the body, acetycholine, that transmits signals between nerve cells. They are used in some drugs, pesticides and chemical nerve agents. Navalny is being treated with the antidote atropine.

The Russian doctors who treated Navalny in Siberia have disputed the German hospital’s conclusion, saying that their tests for cholinesterase inhibitors came back negative.

“There has been some improvement in the symptoms caused by the inhibition of cholinesterase activity,” the Charité Hospital said, as cited by AP and France24.

“While his condition remains serious, there is no immediate danger to his life. However, due to the severity of the patient’s poisoning, it remains too early to gauge potential long-term effects,” it added.

Navalny’s allies insist that he was poisoned with the Kremlin’s support, an accusation rejected by Russian officials.

Western experts have reminded note that Novichok, the Soviet-era nerve agent used to poison former Russian spy Sergei Skripal and his daughter in the UK, was a cholinesterase inhibitor. Another case in hand has been the poisoning of Bulgarian arms producers Emiliyan Gebrev in Sofia back in 2015.

“We have an obligation to do everything so that this can be cleared up,” Merkel told reporters at her annual summer news conference regarding Navalny’s case.

“It was right and good that Germany said we were prepared … to take in Mr. Navalny. And now we will try to get this cleared up with the possibilities we have, which are indeed limited,” she added.

In her words, when there is more clarity about what happened, Germany will try to ensure a “European reaction” to the case.

The office of Russia’s Prosecutor General said on Thursday that a preliminary inquiry launched last week had not found any indication of “deliberate criminal acts committed against” Navalny.

Vladimir Putin’s spokesman Dmitry Peskov also said he saw no grounds for a criminal case until the cause of Navalny’s condition was fully established.

(Banner image: Alexei Navalny’s Twitter profile)