France and Germany said that despite repeated calls Russia has provided "no credible explanation" for what happened.

The Kremlin on Thursday said that "such accusations against the Russian president are absolutely groundless and unacceptable."

"There was a meeting, but one shouldn't call it secret,'' Navalny said in a tweet.

"I still can't do almost anything on my own, but yesterday I managed to breathe on my own for the entire day," he wrote in the Russian-language post.

A German military laboratory previously confirmed the substance in his samples.

Navalny, a prominent critic of President Vladimir Putin, was airlifted to Germany last month after collapsing on a flight.

Alexei Navalny has been in an induced coma in a Berlin hospital since he was flown to Germany for treatment more than a week ago.

Whatever actions Western nations will take about the apparent poisoning of Alexei Navalny, expect Vladimir Putin to swat them aside, Matthew Fisher says.

Officials say investigators In Siberia have been working on "establishing all the circumstances of the incident."

Alexei Navalny's allies say the Kremlin is behind the illness of its most prominent critic, accusations that officials denounced as ``empty noise.''