(Reuters) - Pavel Durov, billionaire founder and CEO of the Telegram messaging app, was arrested at the Bourget airport outside Paris on Saturday evening, TF1 TV and BFM TV said, citing unnamed sources.

TF1 and BFM both said the investigation was focused on a lack of moderators on Telegram, and that police considered that this situation allowed criminal activity to go on undeterred on the messaging app.

Telegram did not immediately respond to a Reuters request for comment. The French Interior Ministry and police had no comment. Russia's Foreign Ministry said it was taking steps to "clarify" the situation and questioned whether Western non-governmental organizations (NGOs) would seek his release..

What is known about Durov and Telegram:

* Russian-born Durov, 39, is founder and owner of messaging app Telegram, a free to use platform that competes with other social media platforms such as Facebook's WhatsApp, or Instagram, TikTok and Wechat. The platform aims to surpass one billion active monthly users within a year.

* Telegram is influential in Russia, Ukraine and the republics of the former Soviet Union. It has become a critical source of information on Russia's war in Ukraine, used heavily by both Moscow and Kyiv officials. Some analysts call the app "a virtual battlefield" for the war.

* Durov, whose fortune was estimated by Forbes at $15.5 billion, left Russia in 2014 after refusing to comply with government demands to shut down opposition communities on his VKontakte social media platform, which he sold.

* Russian and French media say Durov became a French citizen in 2021. He moved himself and Telegram to Dubai in 2017.

* "I would rather be free than to take orders from anyone," Durov told U.S. journalist Tucker Carlson in April about his exit from Russia and search for a home for his company which included stints in Berlin, London, Singapore and San Francisco.

* In the same interview, Durov said that, beyond money or Bitcoin, he had no major property such as real estate, jets or yachts, as he wanted to be free.