Hackers invoked the 9/11 attacks Tuesday in their most chilling threat yet against Sony Pictures, warning cinema-goers not to see a film which has angered North Korea.

There were growing signs that the threat may work, as Sony left it to theater managers to choose whether to show "The Interview," while an industry expert forecast that many would decide it wasn't worth the risk.

"Will theater owners balk at booking the film? It's actually highly possible," analyst Jeff Bock at box office tracker Exhibitor Relations told AFP.

"No one wants another scenario like what happened with 'The Dark Knight Rises' shooting in Colorado," he said, referring to the July 2012 Aurora shooting, in which a gunman killed 12 and injured 70 others.

Sony made no official comment, but a source familiar with its thinking said that the decision whether to show the film "is with theater owners, partners whom we support."

But the stars of the movie, James Franco and Seth Rogen, have canceled all promotional appearance related to the film, according to industry media.

At least one chain, Carmike theaters based in Georgia, said they will not show the movie, according to Variety.

That showbiz industry publication and the New York Times said the New York City premier scheduled for this week at the Landmark chain's Sunshine Cinema had also been cancelled.

Two other major chains, AMC and Regal Theaters, did not immediately respond to AFP requests for comment.

The 9/11 threat -- which was downplayed by US authorities -- came as lawyers filed two class action suits against the embattled studio, claiming it failed to protect employees' data, stolen in a huge cyber-attack three weeks ago.

- 'Christmas gift' -

In a new statement cited by US media, the so-called GOP (Guardians of Peace) hacking group announced the start of a "Christmas gift," including leaked emails from Sony boss Michael Lynton.

Specifically, it warned movie-goers against seeing the comedy about a fictional CIA plot to assassinate North Korean leader Kim Jong-Un. Pyongyang has denied being behind the threats and hacking.

"We will clearly show it to you at the very time and places 'The Interview' be shown, including the premiere, how bitter fate those who seek fun in terror should be doomed to," the latest statement said, again in broken English.

"Soon all the world will see what an awful movie Sony Pictures Entertainment has made. The world will be full of fear," added the statement.

And it warned: "Remember the 11th of September 2001. We recommend you to keep yourself distant from the places at that time. (If your house is nearby, you'd better leave.)"

A red-carpet premiere was held in Los Angeles for the film last week, while another one is scheduled in New York on Thursday.

- Lawsuit targets Sony -

The US State Department played down the threat.

"There is no credible intelligence backing this up at this point in time," State Department spokeswoman Jen Psaki told CNN.

The threat came a day after Sony Pictures boss Lynton sought to reassure employees at a staff meeting, vowing the studio will not be destroyed by the leaks. A day before that hackers promised a big "Christmas gift."

"This will not take us down," Lynton told employees, adding: "You should not be worried about the future of this studio."

The hackers have demanded that Sony stop the release due on December 25 -- Christmas Day -- of the comedy "The Interview."

The movie was originally due out in October. Speculation has grown that its release could be delayed again, although Sony has made no comment or suggestion that it could give in to the hackers' demands.

North Korea has denied involvement in the brazen November 24 cyber-attack, but praised it as a "righteous deed" potentially orchestrated by supporters furious over the movie.

Meanwhile, lawyers said they have filed two class action suits against Sony Pictures in Los Angeles.

One of the lawsuits alleges that "Sony failed to secure and protect its computer systems, servers, and databases, resulting in the release of the named plaintiffs and other class members'" personal data.

"An epic nightmare, much better suited to a cinematic thriller than to real life, is unfolding in slow motion for Sony's current and former employees," said the 45-page lawsuit.