Alexei Navalny. All news about - "Alexei Navalny"
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.
Navalny, who collapsed on a plane from Siberia to Moscow on Aug. 20 and spent nearly three weeks in a coma, was discharged last week from the Berlin hospital where he was being treated.
Tests in Germany, France and Sweden have determined Navalny was poisoned with a Novichok nerve agent and the West has demanded an explanation from Russia.