Russian opposition leader Alexei Navalny was definitely poisoned, German Chancellor Angela Merkel's spokesman Steffen Seibert said Wednesday.

Seibert said that an investigation by a military laboratory found "a chemical nerve agent from the novichok group" in Navalny's body.

Novichok was the nerve agent used in the poisoning of former Russian spy Sergei Skripal and his daughter in Salisbury, Hampshire in 2018.

Navalny was flown to Munich after falling ill on August 20. He is one of the most prominent critics of Russian President Vladimir Putin and has been jailed dozens of times for his activism over the past decade.

A spokesperson for Navalny claimed he had been poisoned the same same day he fell ill.

Last week, the German hospital where Navalny is being treated stated on August 24 that tests indicated he was poisoned.

A day later the Kremlin brushed off allegations that Navalny was the victim of an intentional poisoning orchestrated by authorities, The Associated Press reported.

The Kremlin added there were no grounds for a criminal investigation so far since it hasn't been fully established what caused the politician to fall into a coma.