North Korea's Internet Briefly Went Down Again on Tuesday

Dyn Research said North Korea's online connection, delivered by Chinese communications firm China Unicom, went offline at 1541 GMT and were restored just over an hour later.

They continue to face "connectivity problems" and the brief blackout happened after several hours of an unstable connection, similar to the results of an external attack, the research group said.

On Monday, North Korea had been cut off from the Internet for more than nine hours, triggering speculation that the isolated dictatorship had been targeted by United States authorities.

Washington has accused North Korea of being behind the hacking of Hollywood studio Sony Pictures, and President Barack Obama has promised a "proportionate response" to the alleged attack.

But the US State Department refused to comment Tuesday about whether they were involved in the Internet shutdown.

"The president has spoken to what our potential response is, separate and apart from what we've seen over the last 24 hours," State Department deputy spokeswoman Marie Harf told reporters.

"I leave it to North Koreans to talk about if their Internet was up, if it wasn't, and why."

China has suggested Washington and Pyongyang hold talks over cyberhacking. US officials, however, have dismissed a North Korean proposal for a joint investigation into the Sony hack and instead called for the hermit state to compensate the film studio.

Washington has urged Beijing Pyongyang's closest ally to help rein in the North's cyberhacking activities, with US Secretary of State John Kerry speaking with Chinese Foreign Minister Wang Yi over the weekend to discuss the problem.

"They had a discussion about the issue and I think despite our difference affirmed that malicious cyberactivity like this can pose a risk to international peace and security," Harf said Tuesday.

The cause of the outages in North Korea's already limited Internet access has not been confirmed, but experts said that the kind of crash it suffered resembles that caused by a "denial of service" attack.

North Korea has limited access to the worldwide web with access to just four networks on the global Internet, compared to 150,000 in the United States, analysts say.

Pyongyang's main Internet presence is its Uriminzokkiri website, which has Twitter and Flickr feeds and is best known for posting propaganda videos excoriating South Korea and the United States.