The 44-year-old, who is one of Vladimir Putin’s most outspoken critics, blames Moscow for the attack that nearly killed him, although the Kremlin denies any involvement.
He appeared at an ad-hoc hearing – held in a police station in Khimki, outside Moscow – on Monday afternoon.
In a video posted to Twitter by his spokeswoman Kira Yarmysh, Mr Navalny said: “I don’t understand what’s going on. A minute ago, I was brought from cell here to meet my lawyers.
Crowds of supporters waited to welcome Mr Navalny home
“I came here and here is the Khimki court session taking place. Some strangers are filming me on camera… Why the court session is taking place in police station I cannot understand. Why was no one was informed?
“I have seen a lot of jokes about judicial system here… It’s not possible what is happening here. It’s the highest level of lawlessness. I cannot call it any other word.”
A number of Navalny supporters were detained at Moscow’s Vnukovo airport
Mr Navalny’s detention was widely expected because Russia’s prisons service said he had violated parole terms from a suspended sentence on a 2014 embezzlement conviction.
EU and US demand his release
The United States and several European governments have demanded his release from Russian detention.
US Secretary of State Mike Pompeo said the Russian authorities were trying to silence their critics. He called for Mr Navalny’s “immediate and unconditional release”.
“Confident political leaders do not fear competing voices, nor commit violence against or wrongfully detain political opponents,” Mr Pompeo said.
US President-elect Joe Biden’s incoming national security adviser stuck a similar tone, saying: “The Kremlin’s attacks on Mr Navalny are not just a violation of human rights, but an affront to the Russian people who want their voices heard.”
The response from the EU was equally strong, with France, Italy and the president of the European Commission, Ursula von der Leyen, among those issuing demands for his release.
I condemn the detention of Alexei Navalny by the Russian authorities. They must immediately release him and ensure his safety.
Detention of political opponents is against Russia’s international commitments. pic.twitter.com/RRATmAHVvn
German Foreign Minister Heiko Maas described the arrest as “totally incomprehensible”.
UK Foreign Secretary Dominic Raab said Mr Navalny’s arrest was “appalling” and called for his immediate release.
“Rather than persecuting Mr Navalny, Russia should explain how a chemical weapon came to be used on Russian soil,” he said.
Russia’s foreign minister dismissed the international condemnation.
Sergei Lavrov said Western politicians were using it as a way to “divert attention” from domestic problems.
Russia’s prison service on Sunday said the Kremlin critic had violated the terms of his suspended sentence for embezzlement, and that he would remain in custody until a court ruling.