Anton Nosik's family and friends announced on Sunday that the Russian internet entrepreneur had passed away.

Demyan Kudryavtsevm, a close friend of Nosik's and the current owner of the Moscow Times and Vedomosti business daily, posted on his Facebook page that the former journalist and blogger had died on Saturday night.

Initial reports suggested that he died of a heart attack.

"Nosik was one of the pioneers of the Runet," Vedomosti reported, using the slang term for the Russian-language web.

Russian opposition activist Alexei Navalny described Nosik as his mentor, saying "he had a decisive influence on my views and activities connected to the internet and journalism."

Pioneer of Runet

Nosik founded Gazeta.ru in 1999, one of Russia's first internet news publications, before launching two other popular news sites, Lenta.ru and Newsru.com. His work as a start-up manager and editor later saw him become one of the country's first and most widely read bloggers.

An outspoken Kremlin critic, Nosik would later distance himself from the news websites he had launched, as they became less opinionated and less critical of the Russian government under new ownership.

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As a blogger, Nosik would go on to become one of the most high-profile critics of Russian President Vladimir Putin and his government, in particular of its moves to crack down on internet freedoms.

Deutsche Welle's Russian news department posted a photo of Novik visiting the DW's headquarters in Bonn. 

Head of Deutsche Welle's Russia, Ukraine and Turkey service, Ingo Mannteufel, praised Nosik, saying: "Since 2003, Anton Nosik has been a mentor, partner and very good friend of DW. I am very grateful for all he has done for us. In the name of all his friends at DW, I express our condolences to his family."

Guilty of extremism

Last year, Nosik was found guilty of extremism over a headline on the Live Journal website, in which he wrote "Wipe Syria off the Face of the Earth." He avoided prison but was fined 500,000 rubles ($8,000, 7,260 euros)

Read more: Internet censorship in Russia

Nosik later defended the headline, writing: "My opinion on this issue is that my statements do not contain any extremist views ... I positively do not see any extremism in the fact that I will not feel sorry for the Syrian state."

Article 282 of Russia's criminal code has been increasingly applied in recent years. Once only used against those actually inciting violence, many bloggers and social media users have been charged and often found guilty for merely criticizing Kremlin policy.

Despite his stringent criticisms directed at the Kremlin, even Prime Minister Dmitry Medvedev joined in the tributes, writing on his Facebook page that Nosik "was a real professional, a trailblazer for the Russian internet."

Nosik was born in Moscow and moved to Israel in the early 1990s where he wrote for the Jerusalem Post newspaper. He returned to Russia in 1997, where he worked on the development of Russia's online space.