Paris-Germany on Monday urged Moscow to step up its efforts to investigate the apparent poisoning of opposition leader Alexei Navalny who is currently being treated at a Berlin hospital in a coma. Foreign Minister Heiko Maas said in a special address to French ambassadors in Paris that Europe needed “constructive” relations with Russia for the sake of the continent’s own security but it was clear now that “dark clouds” were hanging over bilateral ties.

“Of course we have the expectation that Russia should contribute more to clearing up of the Navalny case than it is doing at the moment,” he said alongside French counterpart Jean-Yves Le Drian. Berlin’s renowned Charite hospital said on Friday there was “some improvement” in Navalny’s condition but the 44-year-old nevertheless remains in a medically induced coma and on a ventilator. Navalny fell ill after boarding a plane in Siberia earlier this month. 

He was initially treated in a local hospital before being flown to Berlin for treatment. Charite doctors said they believed the anti-corruption campaigner was poisoned with a substance that inhibits the cholinesterase enzyme, a feature of nerve agents.

Navalny’s allies say he may have been poisoned by a cup of tea he drank at Tomsk airport in Siberia. But the Russian doctors who first treated Navalny said their tests did not find any toxic substances, and the Kremlin has rejected international calls for an investigation.