At least five new Sony Pictures movies have been leaked online, reinforcing suspicions that North Korea may have played a role in a cyber-attack in reprisal for Sony's impending release of a film about a plot to assassinate leader Kim Jong-un, news reports said.

Sony has asked for an FBI investigation into the case after last week's hacking knocked down its computer network and pirated versions of five new films, including the recently released "Fury," turned up online over the last few days, according to local news reports.

"Fury," a World War II drama, has received more than 888,000 downloads since Saturday, according to E! News and other media outlets. The other four that have appeared on file-sharing sites are "Annie," "Still Alice," "Mr. Turner" and "To Write Love on Her Arms," according the reports.

The leak is believed to have happened after a massive hacking attack on Sony's computer network that locked Sony employees out of their computers entirely and forced them to resort to pen and paper to do their jobs, according to media reports.

The attack came about a month before Sony's release of "The Interview," which tells the story of two American journalists who land an interview with the North Korean leader in Pyongyang but are then recruited by the CIA to kill him.

North Korea has strongly protested against the movie, calling it "the most undisguised terrorism."

There is no concrete evidence yet pointing to North Korea's involvement, but what's worth noting is that hackers have not chosen to leak the film "Interview," Emma Woollacott, a technology journalist, said in an article on the Forbes website.

"This could suit the North Korean government, as the last thing it wants is for people to see the movie," she said. (Yonhap)