Pavel Durov, 39, holds a French passport in addition to his Russian nationality.
President Emmanuel Macron on Monday denied any political link to the arrest of Telegram founder Pavel Durov as the tech tycoon spent a second day in French custody following his surprise arrest at a Paris airport.
Numerous questions have been raised about the timing and circumstances of Durov's detention.
Sources close to the case said Durov is accused of failing to curb the spread of illegal content on Telegram, which has over 900 million users. The company has dismissed the accusations.
Born in Soviet times into a family of academics in Leningrad, now known as Saint Petersburg, Durov spent his childhood in Italy before building up Russia's then-biggest social network VKontakte (VK) in his early 20s. He set up Telegram after leaving Russia a decade ago and Forbes magazine estimates his current fortune at $15.5 billion.
Writing on the X social media platform that he was addressing "false information" concerning the case, Macron said Durov's arrest "took place as part of an ongoing judicial investigation."
"It is in no way a political decision. It is up to the judges to rule on the matter," he wrote in a highly unusual comment on a legal case.
Durov, 39, holds a French passport in addition to his Russian nationality.
- 'Nothing to hide' -
An investigating magistrate extended Durov's detention on Sunday, according to a source close to the investigation. The initial detention for questioning can last up to 96 hours.
When this period ends, the magistrate can either free Durov or press charges and remand him in custody.
Durov, who has been based in Dubai in recent years, arrived in Paris from the Azerbaijani capital Baku, and was planning to have dinner in the French capital, a source close to the case said.
He was accompanied by a bodyguard and a personal assistant who always travelled with him, added the source, asking not to be named.
One key question is why Durov flew into France when he would have likely been aware he was wanted in the country. "Perhaps he had a feeling of impunity," said a source close to the case, asking not to be named.
Russian President Vladimir Putin was in Baku on a state visit to Azerbaijan on August 18 and 19 but Kremlin spokesman Dmitry Peskov denied that the pair had met.
Durov is accused of failing to take action to curb the criminal use of his platform.
France's OFMIN, an office tasked with preventing violence against minors, issued an arrest warrant for Durov in a preliminary investigation into alleged offences including fraud, drug trafficking, cyberbullying, organised crime and promotion of terrorism, another source said.
Telegram said in response that "Durov has nothing to hide and travels frequently in Europe."
"Telegram abides by EU laws, including the Digital Services Act -- its moderation is within industry standards," it added.
"It is absurd to claim that a platform or its owner is responsible for the abuse of that platform."
- 'Enforce the law' -
Telegram has positioned itself as a "neutral" alternative to US-owned platforms, which have been criticised for their commercial exploitation of users' personal data.
It also plays a key role since Russia's invasion of Ukraine, used actively by politicians and commentators on both sides of the war.
But critics accuse it of hosting often illegal content ranging from extreme sexual imagery to disinformation and also narcotics services.
Kremlin spokesman Peskov said Moscow had received no information from France on why Durov was detained, saying "we do not know concretely what Durov is accused of".
Elon Musk, who leads the Tesla car group and X, formerly Twitter, posted the hashtag #FreePavel on his platform and commented in French, "Liberte Liberte! Liberte?" (Freedom Freedom! Freedom?).
Macron said that while France is "deeply committed to freedom of expression and communication" such freedoms are "upheld within a legal framework, both on social media and in real life".
"It is up to the judiciary, in full independence, to enforce the law," he said.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)