The Kremlin accused specialists at the U.S. Central Intelligence Agency on Thursday of working with Russian opposition politician Alexei Navalny and said Moscow believed he was receiving instructions from people it described as “instructors”.

Navalny told a German magazine he believed Russian President Vladimir Putin was behind his suspected poisoning, but said he was not afraid and that he would return to Russia to resume campaigning.

Kremlin spokesman Dmitry Peskov told reporters the allegation by Navalny was unacceptable, groundless and insulting, but that he was free to return to Russia.