Pavel Durov, the billionaire Russian founder of the Telegram messaging app, has reportedly been arrested at an airport in France.
Mr Durov, who is also the company’s chief executive, was detained after his private jet landed at Bourget, outside Paris.
French media reported that he had been held under an arrest warrant in France as part of a police investigation.
According to reports, the investigation focuses on moderators and criminal activity being carried out on the Telegram platform.
Telegram has not responded to a request for comment.
Russia’s foreign ministry appeared to confirm Mr Durov’s arrest on Sunday morning when a spokeswoman took to Telegram to question whether Western groups would lobby for his release.
“Do you think … they will appeal to Paris and demand Durov’s release, or will keep their lips sealed?,” Maria Zakharova, the spokeswoman said on Telegram messaging app.
The French Interior Ministry and police declined to comment but Russia’s embassy in France said it was taking “immediate steps” to clarify the situation around Mr Durov.
TF1 reported that Mr Durov, 39, had been travelling from Azerbaijan and had been arrested shortly after landing at about 8pm local time (7pm UK).
Mr Durov’s fortune is estimated by Forbes to be worth $15.5 billion (£11.7 billion) and he currently lives in Dubai, where Telegram is based.
He has citizenship in Russia, Saint Kitts and Nevis, the United Arab Emirates and France.
Mr Durov left Russia in 2014 amid a row with the Kremlin over his VK social media platform, which Russian authorities claimed was housing online communities of activists critical of Vladimir Putin.
He has previously revealed that some governments have sought to pressure him over the app, which has now 900 million active users, but he has insisted it remains a “neutral platform” and not a “player in geopolitics”.