'America has lost its first cyberwar': US investigators find North Korea responsible for Sony hacks

US investigators have reportedly found North Korea responsible for the hacker attacks that forced Sony to cancel the theatrical release of its film The Interview, a comedy about the assassination of Kim Jong-Un.

Law enforcement sources told CNN the investigation had discovered the hackers responsible for the company's leaked emails and threats against cinemagoers worked for the rogue state.

A statement is expected by tomorrow.

Former Republican congressman and 2012 Presidential candidate Newt Gingrich said the attack heralded a new era of international conflict.

"With the Sony collapse America has lost its first cyberwar," he tweeted.

"This is a very very dangerous precedent."

The Interview had already premiered in Los Angeles last week, but the film's first New York showing planned for the end of the week has now been cancelled along with its full theatrical release.

A number of major cinema chains, concerned by threats to moviegoers invoking the September 11 attacks, had already dropped the film.

The hacking attacks, which also released a number of embarrassing emails from Sony executive Amy Pascal and producer Scott Rudin to the public, were carried out by a group calling itself the Guardians of Peace.

North Korean leader Kim Jong-Un had earlier denied the cyber-attacks were carried out by his regime, but praised the culprits for their actions.