Pavel Durov, a billionaire tech entrepreneur and Russian exile who founded the encrypted messaging application Telegram, was arrested at the Bourget airport outside Paris on Saturday evening.

Telegram, which enjoys widespread popularity in Russia, Ukraine and Belarus, is ranked as one of the most popular social media sites in the world, trailing only Facebook, TikTok, YouTube, WhatsApp, Instagram and WeChat. The platform is aiming to surpass one billion users at some point next year.

Durov founded the Dubai-based platform after he lost Russia in 2014 for refusing to censor his VK social media platform, which he later sold.

According to French outlets TF1 and BFM, Durov was arrested due to lack of content moderation on Telegram. Police blamed Durov for allowing “criminal activity” to flourish on the app and placed him under arrest.

Telegram has become a main source of uncensored information surrounding the war in Ukraine since Russia invaded the country in 2022. The app has become preferred means of communications for Ukraine’s President Volodymyr Zelenskiy and his officials, Reuters noted.

Russian government officials also use the app to disseminate news. Telegram has become one of the few places where Russian citizens can access information about the war in Ukraine.

The app was previously banned in Russia after Durov refused to hand over user data, though it was eventually unbanned in 2022.

Top-rated conservative commentator Tucker Carlson — who has interviewed Durov — condemned the arrest as an authoritarian power play.

“Pavel Durov left Russia when the government tried to control his social media company, Telegram. But in the end, it wasn’t Putin who arrested him for allowing the public to exercise free speech. It was a western country, a Biden administration ally and enthusiastic NATO member, that locked him away,” Carlson wrote in an X post.

“Pavel Durov sits in a French jail tonight, a living warning to any platform owner who refuses to censor the truth at the behest of governments and intel agencies. Darkness is descending fast on the formerly free world.”

This is a developing story.