Russian social network founder quits amid concern over internet freedom

The founder of Russia's most successful social network has left the company after a protracted dispute with its Kremlin-linked owners, raising questions over internet freedom in the country.

Announcing that he was leaving Vkontakte, Pavel Durov said he had been unhappy with the way the company had been run since its ownership structure changed last year.

"The freedom of action of the chief executive in managing the company has considerably decreased. It has been harder and harder to remain with those principles on which our social network is based," Durov wrote on his personal Vkontakte page.

The statement finished with a quote from The Hitchhiker's Guide to the Galaxy - "So long and thanks for all the fish" - which many initially took to be an April Fools' joke. The company later confirmed that Durov had left.

Vkontakte is popular in Russia and other former Soviet Union countries, where it has more than 100 million users. It is part owned by the Kremlin-friendly oligarch Alisher Usmanov and part by an investment fund thought to have links to the Kremlin.

Durov has rarely given interviews or appeared in public. He is known for occasional extravagant gestures, such as throwing money out of the window of the Vkontakte offices in St Petersburg to delighted passersby.