The company said it "apologises to Britney Spears and her fans for any confusion."

"The Interview", a comedy about the fictional assassination of North Korean leader Kim Jong-Un, has earned more than $15-million in online purchases.

Lauded by moviegoers who champion free speech, the fictional account of two talk show hosts plotting to kill Kim Jong-un was sold out in theatres.

In a move to prove it had nothing to do with the cyber attack on Sony Pictures, North Korea offers its efforts to investigate the matter with the US.

Cyber experts warn that cyber attacks on Sony Pictures, which paralysed computer systems and leaked files, could have been extortion.