BERLIN (AP) — The German hospital treating Russian opposition leader Alexei Navalny says he has been taken out of an induced coma and is responsive.

German experts say Navalny, who fell ill Aug. 20 on a domestic flight in Russia, was poisoned with a substance belonging to the Soviet-era nerve agent Novichok.

Berlin’s Charite hospital said Monday that Navalny’s condition has further improved, allowing doctors to end the medically induced coma and gradually ease him off mechanical ventilation.

It noted that he was responding to speech but “long-term consequences of the serious poisoning can still not be ruled out.”

The German government last week demanded that Russia investigate the case.