Anton Nossik, a Russian Internet entrepreneur who is often referred to as the godfather of the Russian Internet, died on Saturday night.

Nossik, 51, was with friends at a dacha when he suffered a sudden heart attack during the night of July 9, his wife confirmed to RT on Sunday. A prominent public figure and blogger, the news of Nossik's death was met with shock on social media.

"It's impossible to believe," opposition politician Ilya Yashin wrote on Twitter. "Rest in peace, my friend."

Nossik was a widely respected media entrepreneur and the founder of several large news websites such as Lenta.ru and Gazeta.ru.

"It was Nossik who came up with [a vision for] Russian online media, and almost every single big outlet is still the same," fellow blogger and colleague Maxim Kononenko wrote on Lenta.ru.

"Nossik was a family friend," reacted opposition activist Alexei Navalny on his blog. "He greatly influenced my views and actions related to the Internet and journalism. I'm sure many others will say the same. He didn't like it when people called him 'one of the founders of the RuNet,' but that's what he was."