German doctors confirm cholinesterase inhibitors used on Russian opposition leader, similar to nerve agent used to poison Russian spy Sergei Skripal in Britain in 2018

Contradicting Russian doctors, who blamed a metabolic disorder, German medical officials say Putin critic was probably hit by substance that targets central nervous system

Kremlin denies resistance to transfer was political; dissident to be treated at specialist facility after suspected poisoning

Siberian hospital officials assert opposition leader too unstable to be evacuated, while allies assert authorities are stalling to prevent detection of poisoning

While spokeswoman for anti-corruption campaigner points finger at Putin, Moscow says claims of sabotage 'only assumptions' until tests prove otherwise

Spokesperson says Putin critic fell ill on flight, is on a ventilator in intensive care, after apparently consuming toxin that was placed in his tea

Lawmaker revered in Russia as the first woman to fly in space proposes either scrapping two-term limit for presidents or resetting the clock so his four terms wouldn't count

As all allies of opposition figure Alexei Navalny are barred from running in local and regional elections, some say vote has lost legitimacy

Alexy Navalny, one of Putin's most vocal critics, pushes back against claim he had an allergic reaction

Alexei Navalny fell ill while in detention for calling an unsanctioned protest