WASHINGTON (AFP, Reuters) - US President Barack Obama said North Korea's hack of Sony Pictures was an act "cyber vandalism" and not an act of war, according to an interview to air Sunday morning on CNN.

"No, I don't think it was an act of war. I think it was an act of cyber vandalism that was very costly, very expensive. We take it very seriously. We will respond proportionately," Obama told CNN's "State of the Union with Candy Crowley" show.

Obama also said his government was considering putting North Korea back on a US list of countries that sponsor terrorism.

Washington blames North Korea for a cyber security breach at Sony which led to the release of embarrassing emails and caused executives to halt the release of the madcap action film "The Interview". The film about a fictional CIA plot to kill the country's leader infuriated North Korea.

The delay of the film's release sparked political uproar in the US with some politicians claiming North Korea carried out a highly aggressive act. But Obama, who criticised the film's cancellation, stopped well short of calling the cyber attack an act of war.

The president warned that such digital attacks are something the country will have to adapt to. "We're going to be in an environment in this new world where so much is digitalised that both state and non-state actors are going to have the capacity to disrupt our lives in all sorts of ways," Obama said in his appearance on the CNN show.