The US President's Office has waded into the ongoing row over a hack on Sony Pictures, which saw several unreleased films turn up online.

Thousands of sensitive documents from the company were also leaked in the cyber attack, which has been linked to North Korea.

They included an e-mail exchange between Sony executives making derogatory comments about Barack Obama.

Both co-chairman Amy Pascal and producer Scott Rudin have since apologised for the remarks.

In a statement, Ms Pascal said "although this was a private communication that was stolen, I accept full responsibility for what I wrote and apologize to everyone who was offended."

White House spokesman Josh Earnest was asked about the comments at a news conference:

The hack has also seen the leak of negative comments about Angelina Jolie, and potential revelations about upcoming films - including a new Super Mario Bros film and a Men in Black / 21 Jump Street crossover.

North Korea has denied involvement in the hack, but praised the hackers, calling their attack a "righteous deed". North Korean authorities have frequently spoken out against upcoming Seth Rogen and James Franco comedy The Interview, which features a scene where Kim Jong-un is assassinated.