Game of Thrones' fifth season premieres Sunday on HBO, but thousands of fans will have already seen the first episode - and more - thanks to an unauthorized leak.

The first four episodes of Game of Thrones were spotted on torrent sites on Saturday, and were downloaded more than 100,000 times in the first three hours that they were available, Deadline reports.

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On Sunday, HBO addressed the leak (and verified that the episodes were authentic). "Sadly, it seems the leaked four episodes of the upcoming season of Game of Thrones originated from within a group approved by HBO to receive them," the network said in a statement, as reported by Deadline. "We're actively assessing how this breach occurred."

Game of Thrones is currently the most pirated show on television, and is premiering on Sunday night simultaneously in 170 countries in an effort to stop piracy.

Game of Thrones premieres Sunday at 9/8c on HBO.

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