Update, 10 p.m. ET: After more than nine hours and 30 minutes, Internet service has been restored in North Korea, according to technology news service Dyn Research. Access is only partial, Reuters reports, but the country's main news service and newspaper both are back online.

Original post: North Korea's Internet is offline — days after President Obama pledged a "proportional response" to the communist country's alleged hacking of Sony Pictures, multiple news reports say.

Doug Madory, the director of Internet analysis at Dyn Research, told The New York Timesand other news organizations that North Korea's Internet access became unstable late Friday. By Monday, it was offline, he said.

San Francisco-based CloudFlare, a network and security company that monitors global Web access, told The Times that North Korea's Internet access was "toast."

It's unclear what caused the outage, but State Department spokeswoman Marie Harf said today: "We aren't going to discuss publicly operational details about the possible response options or comment on those kind of reports in any way except to say that as we implement our responses, some will be seen, some may not be seen."

In an interview with NPR's Elise Hu, Matthew Prince, chief executive of CloudFlare, pointed to four possible scenarios: North Korea turned off its own Internet; China's upstream provider turned it off; the country's routers failed at an unfortunate time; or it was the result of a denial-of-service attack from either a hacking group or the U.S. Prince said he thinks it's unlikely the U.S. was behind the reported outage.

North Korea has one of the lowest Internet penetrations in the world — with access limited mostly to the country's elite. The U.S. has linked the recent hacking of Sony Pictures to North Korean hackers, though North Korea itself has denied it is responsible — even though it called the act righteous. There are computer security experts who question whether Pyongyang is behind the hack.

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