North Korea Is Experiencing a Full Internet Blackout

North Korea's Internet services went completely off-line Monday, according to multiple network-monitoring companies—a blackout that comes just days after U.S. authorities formally blamed the secretive, authoritarian regime for the recent Sony Pictures Entertainment hack.

The reclusive state began experiencing Internet challenges on Sunday and went completely off the grid Monday, according to New Hampshire-based Dyn Research.

After 24hrs of increasing instability, North Korean national Internet has been down hard for more than 2hrs pic.twitter.com/hDbitXBoqp

— Dyn Research (@DynResearch) December 22, 2014

It remains unclear what is causing the outage, though the timing is likely to fuel speculation that it is a retaliatory move by U.S. authorities. "While we cannot confirm the source of the North Korean Internet outage, we can confirm that a large number of connections have been withdrawn and that North Korea does not currently have access to the Web," a spokeswoman for the Internet company Cloudflare said in a statement.

A White House spokesman declined to comment on the apparent blackout, saying, "We don't have anything additional on North Korea to share 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," a State Department spokeswoman told reporters earlier Monday.

Just hours after the FBI announced on Friday it had definitively concluded that North Korea was behind the devastating cyberattack on Sony, President Obama promised to "respond proportionally and in a manner that we choose," though he elided specifics about what that might entail.

Reports surfaced over the weekend suggesting that the Obama administration was asking China for help to thwart North Korea from launching any future attacks, which Pyongyang had threatened—while maintaining its innocence—after being blamed for the Sony hack.

Nearly all of North Korea's telecommunications services run through China, its neighbor and sole ally. The impoverished country has very limited Internet connectivity, which is concentrated in the hands of a small minority of its citizens.

The White House has been signaling for the past week that it would carry out a response against the actors behind the Sony hack, though it has shied away from being overly bellicose in its rhetoric. Obama told CNN's Candy Crowley in an interview that aired Sunday that the cyber attack amounted to an "act of cybervandalism," but he quickly added that he did not believe it constituted an "act of war." Some lawmakers, including Republican Sen. John McCain, have described the hack as an act of war.

The breach of Sony's computer networks, which began nearly a month ago, has cost the movie studio hundreds of millions of dollars. It culminated in cancellation of the scheduled Christmas Day release of the comedy film The Interview after the hackers, calling themselves "Guardians of the Peace," threatened 9/11-scale violence against moviegoers if the film's premiere went forward.

Sony is currently mulling alternative ways to release The Interview, a comedy that features Seth Rogen and James Franco as dimwitted celebrities who travel to the hermetic country on a secret CIA-backed mission to assassinate its oppressive dictator, Kim Jong-Un. 

Brendan Sasso contributed to this article.