North Korea's access to the Internet has been disrupted, a day after U.S. President Barack Obama promised that Washington would respond proportionally to Pyongyang for the alleged cyberattack that has devastated Sony Pictures.

News of what appears to be a counterattack against North Korea began to emerge Monday as the country's Internet speeds uniformly crawled for the longest period of time since it has been active. From there, Internet access has declined from a trickle to a full-on blockage.

North Korea is "totally offline" now, says Doug Madory, director of Internet analysis at Dyn Research.

''I don't know that someone is launching a cyberattack against North Korea, but this isn't normal for them," says Madory. "Usually they are up solid. It is kind of out of the ordinary. This is not like anything I've seen before."

During a daily briefing, U.S. State Department spokeswoman Marie Harf refused to confirm reports indicating that Washington had launched a cyber counteroffensive against North Korea. Echoing Obama, Harf said the U.S. is considering several routes to respond to the attack on Sony Pictures.

"We aren't going to discuss publicly [any] operational details about the possible response options or comment on those kinds of reports in any way, except to say as we implement our responses, some will be seen and some will not be seen," stated Harf.

North Korea relies on the Internet infrastructure of China's state-run China Unicom. With the FBI recently reaching the conclusion that North Korea has been behind the cyberattack launched against Sony Pictures, the White House has asked China to block any traffic related to the destructive campaign.

North Korea has adamantly denied any role in the attack that leaked more than 27 GB of internal documents from Sony Pictures Entertainment, but Harf said the U.S. government is confident that Pyongyang is behind the security breach.

"We stand by this conclusion," stated Harf. "The government of North Korea has a long history of denying responsibility for destructive and provocative actions. If they want to help here, they can admit their culpability and compensate Sony for the damages that they caused."

Harf acknowledged that Sony Pictures can't legally accept compensation from North Korea, due to U.S. sanctions on the country. But the State Department spokeswoman said that Washington could work out a legal exception to facilitate the the transaction legally, if North Korea ever claimed responsibility for the attack and offered to tender compensation.