Mr Navalny, a fierce critic of Vladimir Putin, was detained for breaking anti-protest laws. He was involved in protests against a decision to bar opposition candidates from local elections. After being treated in Moscow, he was sent back to hospital and wrote on social media: “Are they really such idiots to poison you in a place where suspicions point only at them?”
“It’s a good question.
“For now I can say one thing with certainty: the people in power in Russia are really quite stupid guys.”
It seems to you that in their actions you need to look for secret meaning or a rational purpose. But in fact they are just stupid, malicious and obsessed with money.”
He posted a picture of himself with a puffy face, and claimed two other opposition activists had been poisoned.
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Mr Navalny was unable to open either eye and said his eyes had swollen to the size of table tennis balls.
His lawyer Olga Michailova told reporters: “He was really poisoned by some unknown chemical substance.”
Mr Navalny’s personal doctor, Anastasia Vasilyeva, said concurred with Ms Michailova and had sent samples of hair and a T-Shirt for independent testing and demanded CCTV footage.
The activist had been detained after urging Muscovites to attend a demonstration on Saturday, in which 1,000 people were arrested.
Ms Mikhailova says she would file an appeal to get him released early on health grounds.
Ms Vasilyeva rejected the idea he had an accidental reaction to something he’d come into contact with by accident.
She pondered: “How can you unintentionally poison someone?”
Reports say Nr Navalny had been diagnosed with allergic dermatitis and suffered a chemical burn to his right eye two years ago but had his vision restored.