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

He had been due to speak at the Oslo Freedom Forum on Tuesday, addressing the annual gathering on the subject of free speech, surveillance and digital rights.

But organisers the Human Rights Foundation said he had been stopped from travelling in person by a French court.

He will now address the event virtually, they added.

"It is unfortunate that French courts would block Mr Durov from participating in an event where his voice is so needed," HRF founder and CEO Thor Halvorssen said.

"Technologies like Telegram are basic tools for those resisting tyranny. This is more than a disappointment for our community; it is a setback for freedom."

In March, Durov was allowed to leave France and travel to Dubai, where his company is based.

Earlier this week however, he was stopped from going to the United States to talk with investment funds.

Since his arrest, Durov had appeared to bow to Paris's demands for stronger efforts to ensure illegal content -- such as child abuse and drug trading -- was not on Telegram.

But he has also alleged that the head of France's DGSE overseas intelligence service had asked him to ban pro-Russian accounts from the platform before recent presidential elections in Romania.

The DGSE has rejected the claims.