A critic of President Vladmir Putin who fell into a coma in Russia and is being treated in Berlin was poisoned with a Soviet-style Novichok nerve agent, a German government spokesman said on Wednesday.
Tests on blood samples conducted at a German military laboratory produced "unequivocal evidence" that Alexei Navalny, Russia's most prominent opposition figure, had been poisoned with Novichok, Steffen Seibert said in an emailed statement.
An agent of the same family was used two years ago to poison a Russian defector living in Britain.
"The federal government will inform its partners in the EU and NATO of the results of the investigation," Seibert added. "It will discuss an appropriate joint response with the partners in the light of the Russian response."
Russia is already under Western sanctions after its annexation of Crimea from Ukraine six years ago, and another stand-off with European nations or the United States may hurt its economy further.
The Russian rouble extended losses against the euro after the German government statement.
Navalny, 44, was airlifted to Germany late last month after collapsing during a flight from the Siberian city of Tomsk to Moscow.
A Kremlin spokesman said Germany had not informed it that it believed Navalny had been poisoned with Novichok, according to the RIA news agency.
Novichok is a deadly group of nerve agents developed by the Soviet military in the 1970s and 1980s.
Britain says Russia used Novichok to poison former spy Sergei Skripal and his daughter in the British city of Salisbury in 2018. Russia has repeatedly denied any involvement in the attack, which the Skripals survived. One member of the public was killed.
"It is a shocking event that Alexei Navalny has become the victim of an attack with a chemical nerve agent in Russia," Seibert said. "The federal government condemns this attack in the strongest terms."