WASHINGTON >> North Korea experienced sweeping and progressively worse Internet outages extending into Monday, with one computer expert saying the country’s online access is “totally down.” The White House and the State Department declined to say whether the U.S. government was responsible.

President Barack Obama said Friday the U.S. government expected to respond to the hacking of Sony Pictures Entertainment Inc., which he described as an expensive act of “cyber vandalism” that he blamed on North Korea. Obama did not say how the U.S. might respond, and it was not immediately clear if the Internet connectivity problems represented the retribution. The U.S. government regards its offensive cyber operations as highly classified.

“We aren’t going to discuss, you know, publicly operational details about the possible response options or comment on those kind of reports in anyway except to say that as we implement our responses, some will be seen, some may not be seen,” State Department spokeswoman Marie Harf said.

North Korea has forcefully denied it was responsible for hacking into Sony. But the country has for months condemned the “The Interview,” a Sony satirical comedy about a plot to assassinate the North Korean leader. Sony canceled plans to release the movie after a group of hackers made terroristic threats against theaters that planned to show it.

North Korean diplomat Kim Song, asked Monday about the Internet attack, told The Associated Press: “I have no information.”

Doug Madory, the director of Internet analysis at Dyn Research, an Internet performance company, said Monday the problems began over the weekend and grew progressively worse to the point that “North Korea’s totally down.”

Residents of the country have only limited Internet access, especially compared to the U.S. But with the current outages, Madory said, “They have left the global Internet and they are gone until they come back.”

Another Internet technology service, Arbor Networks, which protects companies against hacker attacks, said its monitoring detected denial-of-service attacks aimed at North Korea’s infrastructure starting Saturday and persisting Monday. Such attacks transmit so much spurious data traffic to Internet equipment that it becomes overwhelmed, until the attacks stop or the spurious traffic can be filtered and discarded to allow normal connections to resume.

Madory said one benign explanation for the problem might be that a router suffered a software glitch, though a cyber-attack involving North Korea’s Internet service was also a possibility. Routing instabilities are not uncommon, but instead of getting better, as one might expect, “it’s getting worse, getting progressively degraded,” Madory said.

“This doesn’t fit that profile,” of an ordinary routing problem, he said. “This shows something getting progressively worse over time.”