No indication as to whether a cyber-attack caused outage, and if so who might have been behind it

North Korea’s tiny internet network appeared to be working again on Tuesday following a near 10-hour shutdown, amid a row with the US over a hack against Sony Pictures that Washington has blamed on Pyongyang.

There was no indication as to whether a cyber-attack caused the outage, and if so who might have been behind it. The White House and the Department of State declined to comment.

US tech companies monitoring the North Korean web network, which has only about 1,000 web addresses and is accessible only to a handful of elite officials, said it appeared to have suffered a concerted denial-of-service attack, in which a target’s internet equipment is overwhelmed by spurious traffic.

Websites such as those of the official Korean Central News Agency and the Rodong Sinmun newspaper went down during the outage. On Tuesday, US computer experts said the network appeared to have been resurrected.

Jim Cowie, chief scientist at Dyn Research, a US internet analysis company, said in an online post that the entire North Korean internet “went dark” following instability that began at the weekend and seemed “consistent with a fragile network under external attack”. However, he added, it could also have been caused by a technical fault such as a power problem.

In an update, Cowie said the network was now functioning again following a nine-and-a-half-hour shutdown. He told Reuters: “We’re yet to see how stable the new connection is. The question for the next few hours is whether it will return to the unstable fluctuations we saw before the outage.” North Korean websites were again accessible.

The issue of who carried out a cyber-attack, if there was one, is complicated by the fact that knocking out North Korea’s web network would not be a particularly difficult task. It has a total of 1,024 IP addresses – in a country of 25 million people – a single service provider and one connection to the outside world, via China. “Any one of us that was upset because we couldn’t watch the movie, you could do that,” said Dan Holden, director of security research at Arbor Networks. “Their internet is just not that sophisticated.”

Nonetheless, some suspicion is likely to fall on the US after Barack Obama said on Friday that the US government expected to respond to the hacking of Sony Pictures and a subsequent threat against filmgoers which prompted Sony to cancel the release of The Interview, a comedy drama centred on a plot to assassinate the North Korean leader, Kim Jong-un.

Obama did not say what steps might be taken. A state department spokeswoman, Marie Harf, said: “We aren’t going to discuss, you know, 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.”

North Korea, which reveres Kim and his predecessors, Kim Jong-il and Kim Il-sung, as near deities, has reacted with fury to The Interview. It has denied any connection to the Guardians of Power, an anonymous hacking group that claimed responsibility for the theft of a huge cache of emails from Sony, but has praised the hack as a “righteous deed”.

On Monday North Korea again denied being behind the Sony hack, and issued unspecified threats of action against the US after saying it had “clear evidence” that Washington was heavily involved in devising the plot of The Interview.

A statement from the country’s National Defence Commission said North Korea had “already launched the toughest counteraction” to the film, without specifying what this might involve. “Nothing is [a] more serious miscalculation than guessing that just a single movie production company is the target of this counteraction. Our target[s are] all the citadels of the US imperialists who earned the bitterest grudge of all Koreans,” it said.

It is not known how many people in North Korea have access to the internet, but given the tiny extent of the network it is believed to run to just a handful of people among the political elite. Mobile phones are becoming more common in the country, but these are not able to make overseas calls or access the web.

North Korea also has its own very tightly regulated intranet called Kwangmyong, or Bright, to which a slightly larger elite group has access. This provides a connection between industry, universities and government, and is believed to be used mainly to pass information rather than entertainment or commerce.