Tests have shown the critic of Russian President Vladimir Putin was poisoned with a nerve agent from the Novichok group, German Chancellor Angela Merkel’s spokesman Steffen Seibert said.
Mr Navalny is being treated in hospital in Berlin after falling ill during a flight last month.
Mr Seibert said: “It is a shocking event that Alexei Navalny has become the victim of an attack with a chemical nerve agent in Russia.
“The federal government condemns this attack in the strongest terms.”
He added that Germany will inform the EU and NATO.
Mr Seibert said: “The federal government will inform its partners in the EU and NATO of the results of the investigation.
“It will discuss an appropriate joint response with the partners in the light of the Russian response.”
The Kremlin said it had not been informed that Germany believed Mr Navalny had been poisoned with Novichok.
The Russian opposition leader became unwell on a flight from Siberia to Moscow on August 20.
He was moved to Germany for treatment and remains in a coma.
Novichok was used to poison former Russian spy Sergei Skripal in Salisbury in 2018.
Novichok is a deadly group of nerve agents developed by the Soviet military in the 1970s and 1980s.
More to follow…