It is extremely rare for Ilya Yashin, a fierce critic of Vladimir Putin who was recently released from prison, and Margarita Simonyan, a rabid Kremlin propagandist, to find common ground.

But in the hours after the surprise arrest of Pavel Durov, the reclusive founder of the Telegram messaging app, both Yashin and Simonyan – along with thousands of other Russians across the political spectrum – united in demanding his release, underscoring the unique place Telegram holds as Russia’s most popular messaging app.

On Monday evening, prosecutors in France announced that Durov was being held in connection with an investigation into criminal activity on the platform and a lack of cooperation with law enforcement. The Paris prosecutor, Laure Beccuau, said the investigation concerned crimes related to illicit transactions, child sexual abuse, fraud and the refusal to communicate information to authorities.

“I do not consider Pavel Durov to be a criminal and I hope he will be able to prove his innocence in court,” Yashin wrote on X on Monday.

The sentiment was echoed across the opposition, who first came to admire Durov when, as the 27-year-old CEO of the social media platform VKontakte, he received a request from the FSB to take down the pages of opposition groups.

Durov refused and would eventually be forced to sell VKontakte to the state, making him a rare tech mogul to defy the Russian authorities.

His next project, the messaging app Telegram, was built on the principle of user privacy. It also introduced “channels” that allow moderators to quickly disseminate information to large numbers of followers, combining the reach and immediacy of a Twitter/X feed with the focus of an email newsletter – features that have made it a key platform for organising anti-Putin protests.

Despite growing rumours that Durov may have fallen under the Kremlin’s influence, Telegram has remained the primary channel for dissent in Russia, especially after the outbreak of the war, as Putin cracked down on independent media outlets and banned western social media platforms.

Many in the Russian opposition therefore quickly expressed concerns that Durov’s cooperation with French authorities could prompt Moscow to shut down the platform domestically or open the door to similar demands to gain access to Telegram from the Russian government.

For the Kremlin, which has repeatedly clashed with Durov and unsuccessfully tried to ban Telegram, the arrest presented a surprising propaganda coup.

On state talkshows and in print media, Durov’s detention has been portrayed by Russian officials as an example of western hypocrisy over free speech. Kremlin propagandists also quickly put forward unfounded theories suggesting that western intelligence agencies orchestrated Durov’s arrest to gain access to Telegram’s “keys”, including private chats and data of millions of Russians.

“Everyone who is used to using the platform for sensitive conversations should delete those conversations right now and never do it again,” warned Kremlin propagandist Simonyan in a Telegram post.

“Durov has been shut down to get the keys. And he’s going to give them.”

Baza, a Telegram channel affiliated with Russia’s security apparatus, reported that the defence ministry, prominent businessmen, and officers from several security agencies were swiftly instructed to delete work-related messages from the app.

With Durov’s fate in question, so too is the future of Telegram. Analysts believe that the arrest could hinder Telegram’s future fundraising efforts and undermine its financial stability.

There are also growing concerns about the app’s ability to maintain its core privacy protections, particularly after reports from French media that law enforcement agents are trying to access Telegram’s database of private chats.

The potential collapse of Telegram – which by early 2023 handled up to 80% of Russia’s total messenger traffic – could have a far-reaching impact on Russian society.

One group particularly concerned with Durov’s arrest is the Russian military, along with a cohort of pro-war bloggers and reporters who have gained prominence by covering the conflict on Telegram.

Since the start of Russia’s full-scale invasion in February 2022, Telegram has served both as a communication tool within the Russian army and as a platform for the Kremlin to convey its narrative of the war to ordinary Russians.

“They practically detained the head of communications for the Russian army,” lamented the popular Russian military blogger channel, Povernutie na Z Voine, in a Telegram post.

Ordinary Ukrainians and the country’s military also use Telegram to raise funds for the army and blog about the war. However, for internal communications, the army is known to primarily rely on the Signal platform.

Rybar, a leading military analyst close to the Russian leadership described Telegram as “perhaps the main means of units’ command and control”.

Rybar added that Durov’s arrest has exposed the weaknesses in Russia’s communication channels and underscored the urgent need to develop state-controlled apps.

“It would be both quite sad and somewhat amusing if Durov’s arrest turned out to be the catalyst for changes in communication within the Russian armed forces,” he concluded.