Mr Zuckerberg has recounted how he too had received terror threats. "A few years ago, an extremist in Pakistan fought to have me sentenced to death because Facebook refused to ban content about Mohammed that offended him. We stood up for this because different voices -- even if they're sometimes offensive -- can make the world a better and more interesting place," he writes.
He has called for a rejection of "a group of extremists trying to silence the voices and opinions of everyone else around the world," and has pledged that he will not allow that to happen on Facebook.
"I'm committed to building a service where you can speak freely without fear of violence," he says, noting that Facebook follows the laws of different countries, "but we never let one country or group of people dictate what people can share across the world."
He ends by saying, "My thoughts are with the victims, their families, the people of France and the people all over the world who choose to share their views and ideas, even when that takes courage."
On Wednesday, masked gunmen broke into the Paris office of French satirical newspaper Charlie Hebdo when a editorial meeting was on and shot dead 12 people, including some of France's best known cartoonists.
The left-leaning newspaper had repeatedly published controversial cartoon sand caricatures of the Prophet Muhammad.
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