German Foreign minister Heiko Maas said there would be diplomatic consequences for Russia if Kremlin critic Alexei Navalny’s case proves to be state-initiated murder attempt.

Navalny is in stable condition with symptoms receding, though his health status is still serious.

Russain opposition politician and anti-corruption campaigner Alexey Navalny’s condition remains in serious but stable, and the Russian his symptoms of poisoning are receding, according to the Berlin hospital Charité where he is treated after the evacuation from Omsk.

Navalny became criticially ill on a flight from the Siberian city of Tomsk to Moscow last week. After the urgent landing he was treated in local hosiptal in Omsk, and further, upon the request of his family, he was flown to the German capital for treatment.

Doctors at Berlin’s Charite hospital said he was exposed to a cholinesterase inhibitor, a chemical group that includes some nerve agents, though the exact compound hasn’t yet been identified.

According to Russain media the laboratories, investigating the Navalny case, demanded military experts opinon.