Durov, 40, was sensationally detained in Paris in 2024 and is under formal investigation by French authorities over illegal content on his popular messaging service.

Arriving at the Paris courthouse on Monday morning with four of his lawyers, the Russian-born entrepreneur faced his third round of questioning since being charged with multiple infractions linked to enabling organised crime.

Durov, who holds French and Russian passports, has been accused of complicity in running an online platform that allowed illicit transactions, child sex abuse images and other illegal content.

Durov has denied the claims, and his lawyers said in a statement that Monday's full-day session allowed Durov "to provide additional explanations demonstrating the inanity of the facts that are the subject of the investigation".

In his initial questioning in December 2024, Durov denied creating Telegram for illicit use but acknowledged a growing criminal presence on the platform, and pledged to strengthen moderation.

French judicial authorities have noted an improvement in cooperation with Telegram since Durov's arrest, sources involved in organised crime cases told AFP.

Durov, who was initially banned from leaving France, had his judicial control relaxed from early July, allowing him to reside in the United Arab Emirates for a maximum of two weeks at a time.

Durov's lawyers have filed motions to dismiss the charges with the Paris Appeals Court, according to a source close to the case.

"We firmly contest the legality of our client's indictment and that of the numerous investigative acts carried out in defiance of domestic and European law," his lawyers said in their statement Monday.

The lawyers have also filed a legal challenge in France to test the constitutionality of the case, along with a request for a preliminary ruling from the European Union's top court, according to the same source.