BERLIN: Germany said Wednesday that Russian opposition leader Alexei Navalny was poisoned with a Novichok nerve agent, leading Chancellor Angela Merkel to demand answers from the Kremlin and sparking condemnation in Europe.

"It is certain that Alexei Navalny is the victim of a crime. He was meant to be silenced and I condemn this in the strongest possible terms, on behalf of the German government," Merkel said.

The latest in a long line of attacks on Russian defectors and opposition figures sent tensions between Moscow and its EU partners spiralling, with Merkel saying there are now "some very serious questions that only Russia can and must answer." British Foreign Secretary Dominic Raab said that Russia "must tell the truth" about what happened, while the European Union chief Ursula von der Leyen criticised a "despicable and cowardly act - once again". The German government said in a statement issued earlier Wednesday that tests carried out by its armed forces' chemical weapons laboratory found "unequivocal evidence" from samples taken from Navalny that the military-grade Novichok agent was used. The nerve agent is a military-grade poison that was developed by the Soviet government towards the end of the Cold War and can be deployed in an ultra-fine powder, liquid or vapour.

It was used against against ex-double agent Sergei Skripal in Britain in 2018, a poisoning that the West believes was ordered by the Kremlin. Navalny, 44, fell ill after boarding a plane in Siberia last month. He was initially treated in a local hospital before being flown to Berlin for treatment The Kremlin, which has previously questioned the credibility of German doctors, said Russia was ready to cooperate fully.

The Charite hospital on Wednesday reported improvements in Navalny's recovery but said he remains in a serious condition.