Microsoft agreed Monday to buy the Swedish group behind the hugely popular video game "Minecraft" for $2.5 billion, bolstering the increasingly important gaming division of the US tech giant.

The deal for Swedish-based Mojang gives Microsoft one of the best-known video games of all time -- one which is played on game consoles as well as PCs and mobile devices.

Mojang will be merged into Microsoft Studios, which includes the studios behind global franchises including "Halo."

"Gaming is a top activity spanning devices, from PCs and consoles to tablets and mobile, with billions of hours spent each year," said Microsoft chief executive Satya Nadella, announcing the deal.

"Minecraft is more than a great game franchise -- it is an open world platform, driven by a vibrant community we care deeply about, and rich with new opportunities for that community and for Microsoft."

Minecraft is often described as digital Lego. Players try to survive in a hostile world populated by monsters while building tools and buildings and redesigning the environment as they progress.

Despite less sophisticated graphics than many successful competitors, the game has succeeded in winning over children and more seasoned gamers.

Since its launch in 2009, Minecraft has been downloaded some 100 million times on PCs, has been the most popular game on Microsoft's Xbox and is the top paid app for both iOS and Android, according to Microsoft.

"The 'Minecraft' community is among the most active and passionate in the industry, with more than two billion hours played on Xbox 360 alone in the past two years," Microsoft said.

Microsoft plans to continue to make the game available across all the platforms on which it is available today: PC, iOS, Android, Xbox and PlayStation.

- 'Belongs to all of you' -

Mojang's Owen Hill said Minecraft's main creator Markus Persson, who uses the nickname "Notch," decided "that he doesn't want the responsibility of owning a company of such global significance."

"Minecraft has grown from a simple game to a project of monumental significance," Hill said in a blog post.

"Though we're massively proud of what Minecraft has become, it was never Notch's intention for it to get this big."

Indeed, Persson said in his own blog post it was time to move on.

"I don't make games with the intention of them becoming huge hits, and I don't try to change the world," he said.

"Thank you for turning Minecraft into what it has become, but there are too many of you, and I can't be responsible for something this big. In one sense, it belongs to Microsoft now.

"In a much bigger sense, it's belonged to all of you for a long time, and that will never change."

The Swedish group said that "the vast majority (if not all) Mojangstas will continue to work at Mojang for the time being" but that the three founders are leaving.

"We don't know what they're planning. It won't be Minecraft-related but it will probably be cool," Hill said in his blog post.

Forrester Research analyst James McQuivey said the deal has enormous potential for Microsoft if it manages the game wisely.

"Minecraft is what it is because its users are free to make it whatever they want it to be," McQuivey said.

"Will Microsoft be able to let the people run free with Minecraft the way the founders did and continue to do? The right answer, to preserve the value of the property, is 'yes'," he said.

"But that is not usually the corporate answer, whether at Microsoft or elsewhere. Lesson to Microsoft: Let Minecrafters be Minecrafters, or you'll practically guarantee an explosive collapse."

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MICROSOFT