North Korea blames US for Internet outages, calls Obama a 'monkey'

North Korea called US President Barack Obama a "monkey" as it blamed Washington Saturday for Internet outages that it has experienced amid a confrontation with the United States over the hacking of the film studio Sony Pictures.

The National Defence Commission, the North's ruling body, chaired by state leader Kim Jong Un, said Obama was responsible for Sony's belated decision to release the action comedy "The Interview", which depicts a plot to assassinate Kim.

"Obama always goes reckless in words and deeds like a monkey in a tropical forest," an unnamed spokesman for the commission said in a statement carried by the official KCNA news agency, using a term seemingly designed to cause racial offence that North Korea has used before.

Sony cancelled the release of the film when large cinema chains refused to screen it following threats of violence from hackers, but then put it out on limited release after Obama said Sony was caving in to North Korean pressure.

Obama promised retaliation against North Korea, but did not specify what form it would take.

North Korea's main internet sites experienced intermittent disruptions this week, including a complete outage of nearly nine hours, before links were largely restored on Tuesday.

In the statement on Saturday, the North again rejected an accusation by the US Federal Bureau of Investigation that North Korea was behind the cyberattack on Sony Pictures, and demanded that United States produce evidence for its accusation.

The National Defence Commission also dismissed US denials of involvement in North Korea's Internet outage.

"The United States, with its large physical size and oblivious to the shame of playing hide and seek as children with runny noses would, has begun disrupting the Internet operations of the main media outlets of our republic," it said.

In a separate commentary, the North denied any role in cyberattacks on South Korea's nuclear power plant operator, calling the suggestion that it had done so part of a "smear campaign" by unpopular South Korean leaders.

A South Korean official investigating the attacks this week, which led to leaks of internal data from Korea Hydro and Nuclear Power, said authorities were not ruling out North Korean involvement.

"The South Korean puppet authorities are working hard to link this case with (us) though the truth about it has not been probed," Minju Joson, the official publication of the North's cabinet, said in a commentary carried by KCNA.