A Russian court Monday postponed the beginning of an "extremism" hearing against the political network of jailed Kremlin critic Alexei Navalny, part of a campaign to sideline opposition to President Vladimir Putin.
As the proceedings got underway, prosecutors submitted additional documents pushing the start date of the trial to June 9, lawyers representing Navalny's organisations said.
The proceedings, which are being held behind closed doors, are part of a sweeping crackdown on Putin's most prominent critic who was jailed this year and survived a poisoning attack in August.
As part of the effort -- which comes a few months before parliamentary elections -- the lower house is set on Tuesday to begin debating a bill banning members of "extremist" organisations from being elected lawmakers.
Navalny's network is being represented by lawyers of Team 29, a Saint Petersburg-based group that specialises in freedom of speech and treason cases.
The lawyers said it was not clear why Monday's hearing was closed to the public or why some of the case files were labelled secret.
An aide to Navalny Ivan Zhdanov speculated on Twitter that it was an attempt to conceal the "absurdity of what is happening".
Prosecutors in April requested that Navalny's regional network and his Anti-Corruption Foundation (FBK) be designated "extremist" organisations, accusing them of plotting to stage a Western-backed uprising in Russia.
Such a ruling would put Navalny, his supporters and financial backers on par with the Islamic State group and Al-Qaeda, threatening them with long prison sentences.
"The opposition will be crushed," Abbas Gallyamov, an independent political analyst and former Kremlin speechwriter, told AFP.
But "by destroying the opposition, they are destroying their own legitimacy", he added, referring to authorities.
Navalny emerged as an opposition figurehead a decade ago, leading huge anti-Kremlin rallies sparked by claims of electoral fraud in 2011.
Established in 2011, the Anti-Corruption Foundation has published numerous investigations into the lavish lifestyles of Russia's elite.
- 'Sliding into darkness' -
While authorities had for years tolerated Navalny's political movement, analysts say the Kremlin is willing to take no chances ahead of parliamentary elections in September as public fatigue is growing with Putin's two-decade rule.
A Team 29 lawyer said Monday that the crackdown on Navalny's groups was linked to the upcoming elections.
"Members of FBK are now the most popular candidates," Ilya Novikov told journalists outside the court on Monday.
For the authorities, "it's very important to stop these candidates", he added.
Navalny, who is currently in a penal colony outside Moscow, said in a recent Instagram post that Russia was "sliding into darkness".
"But those who are pushing the country backwards are historically doomed."
Ahead of Monday's court hearing, Russia's financial monitoring service Rosfinmonitoring added Navalny's political network to its database of terrorist and extremist organisations.
Navalny's network had disbanded ahead of the listing to shield its members and supporters from possible prosecution.
Lawmakers also proposed legislation that would apply retroactively and ban Navalny's allies from running in parliamentary elections for several years.
The legislation could affect senior members and activists of Navalny's political network and also tens of thousands of Russians who supported its work with donations.
Navalny was arrested in January upon returning from Germany after recovering from a poisoning attack he says was orchestrated by the Kremlin. The Kremlin denies the allegation.
He is serving two-and-a-half years on embezzlement charges in a penal colony about 100 kilometres (62 miles) east of Moscow.