North Korea's Internet went dark for several hours amid rumors of US retaliation over its alleged hacking of a Hollywood studio, just as the pariah state came under attack at the UN over its rights record. It was not clear who or what had shut down Pyongyang's web connections, but cyber experts said the country's already limited Internet went completely offline overnight from Monday to Tuesday local time. Piling further pressure on Kim Jong-Un's regime, UN members debated North Korea's brutal treatment of its huge prison population after China, its sole ally, was rebuffed in a bid to shelve the issue. US-based Internet analysts Dyn Research said Pyongyang's four online networks, all connected through Chinese telecom provider China Unicom, had been offline for nine hours and 31 minutes before services resumed on Tuesday morning. Dyn Research said Pyongyang's very limited infrastructure could be vulnerable to power outages but that the way it had collapsed "seems consistent with a fragile network under external attack."