Super 8" director JJ Abrams (L), stars Elle Fanning and Joel Courtney, and producer Steven Spielberg introduce a clip from the film at the 2011 MTV Movie Awards in Los Angeles, June 5, 2011.[Photo/Agencies]?

Amid rumblings about its low-key marketing campaign, "Super 8" will come out in movie theaters one day ahead of schedule on Thursday as part of a promotional campaign targeted at Twitter users.

Paramount Pictures and Twitter said on Wednesday the sci-fi mystery will open in about 300 theaters across the United States and Canada. It expands to a total of more than 3,000 theaters on Friday.

A hashtag, #Super8Secret, has been given top billing on Twitter's list of most widely followed topics, and users can click on the link to buy movie tickets online, and get free popcorn.

The hope is that they will create an online buzz by sharing their passion for the movie with other Twitter users. The promotion marks the first time Twitter has hosted a sneak preview. It teamed up with Paramount in March to premiere the "Super 8" trailer.

Early reviews have been favorable, but "Super 8" could do with a promotional boost. The $50 million movie arrives in theaters shrouded in such secrecy that it may prove a hard sell in a summer bursting with familiar superheroes and sequels.

The plot centers on a group of kids in a small Ohio town who spend the summer of 1979 making a home movie using the titular 8mm film format that was popular back then. They witness a train crash, which triggers a series of inexplicable events and disappearances.

J.J. Abrams wrote and directed the film, while his mentor Steven Spielberg helped him shape the story and served as a producer. But with no big stars and a trailer that does not show the sci-fi alien creature around whom the film revolves, the buzz for the picture has hardly been deafening, despite some good early reviews.

Yet keeping that mystery element intact is exactly what Abrams wanted, much to the dismay of Paramount executives.

"My feeling is that if you show them (the moviegoers) everything, they won't want to go see it, so there's a battle internally," Abrams told Reuters in a recent interview.

Industry website Deadline Hollywood reported this week that audience awareness of the film is lagging in key categories behind such upcoming movies as "Green Lantern" and "Cars 2."

Paramount, as studios often do, is playing down opening-weekend expectations. The Hollywood Reporter said on Monday that the studio hopes it will earn $25 million to $30 million during its first three days of release across the United States and Canada.