They have since demanded an explanation from Moscow on its attempt to “silence” the Russian opposition leader.
Forty-four-year old Alexei Navalny is the latest Russian defector and Putin critic to be poisoned in suspicious circumstances. He is now receiving medical treatment at a Berlin hospital.
Medical tests from the German military's chemical weapons laboratory had given "unequivocal evidence" that Navalny had been afflicted by military-grade Novichok, a poison first developed by the Soviet Union towards the end of the Cold War.
The findings had prompted "some very serious questions that only Russia can and must answer", German Chancellor Angela Merkel said.
"It is certain that Alexei Navalny is the victim of a crime," she added. "He was meant to be silenced and I condemn this in the strongest possible terms."
The news prompted a fresh round of condemnation from European leaders in an affair that has already sent tensions spiraling between Russia and the West.
British Prime Minister Boris Johnson said Navalny's poisoning was "outrageous", while French Foreign Minister Jean-Yves Le Drian denounced the attack "shocking and irresponsible".
European Union chief Ursula von der Leyen criticized a "despicable and cowardly act — once again".