WASHINGTON/LOS ANGELES (REUTERS) - Faced with the most destructive cyberattack of a company on US soil, President Barack Obama resorted to humour to explain an absurd plot that even Hollywood did not see coming.

In his rebuke of Sony Pictures' decision to shelve "The Interview," about a fictitious plot to assassinate North Korean leader Kim Jong Un, Obama said the public did not have to look farther than the film's stoner-comedy stars to gauge its threat.

"I think it says something interesting about North Korea that they decided to have the state mount an all-out assault on a movie studio because of a satirical movie starring Seth Rogen and James (Franco)," Obama said to laughter at his year-end news conference, which was dominated by the cyberattack blamed on Pyongyang.

But while Obama got laughs in Washington, Oscar winners George Clooney and Sean Penn launched broadsides against Sony and Hollywood studios' response to the hack.

"We cannot be told we can't see something by Kim Jong Un. ... We have a responsibility to stand up against this," Clooney said in an interview with trade publication Deadline.com.

Sony has said it could not release the film on its set date of Dec 25 after cinemas said they would not show it because of fears of unspecified threats from hackers.

Clooney, whose past two films for which he was the director were released by Sony, criticised Hollywood's corporate elite for not supporting the studio after the hack began last month.

He said no one in the industry would sign a petition he and his agent circulated against the hack that disabled Sony's computer network and led to the leak of embarrassing emails.

Penn said in a statement to magazine Mother Jones that scuttling "The Interview" left Hollywood vulnerable to future attacks.

"This week, the distributors who wouldn't show 'The Interview' and Sony have sent ISIS a commanding invitation,"Penn said referring to the Islamic militant organisation.

"I believe ISIS will accept the invitation. Pandora's box is officially open."

After more than three weeks and a notable silence from the film studios, their trade group, the Motion Picture Association of America, issued its first statement on the hack, calling it a"despicable, criminal act."

The Directors Guild of America said "the incident becomes a rallying point for all of us who care about freedom of expression."

Sony's chief executive, Michael Lynton, said the studio was still trying to find a way to distribute the film.