Captain America (Chris Evans), Iron Man (Robert Downey Jr) and Thor (Chris Hemsworth) lead the comic book team's lineup, with Hulk (Mark Ruffalo), Hawkeye (Jeremy Renner) and Black Widow (Scarlett Johansson) joining the ensemble.
The new extended video is the final trailer before the blockbuster opens in UK cinemas on April 26 and May 4 in the US. The movie, which debuted a theatrical poster this week, has officially been retitled Marvel Avengers Assemble in the UK.
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The Avengers visual effects chief Chris Wells recently said that the film will "dwarf" other movies in the genre, adding that fans of the Hulk will be particularly impressed with the portrayal of the character.
"For people who enjoy the comics and haven't really liked the way some of the characters were treated in other movies, I think they're going to be a little more appeased by this one. Especially the Hulk," he said.
"They let the Hulk be Hulk and that's great. He acts more like the comic book Hulk. It's fun. My biggest problem with every single superhero movie is I don't think the payoff ever matches the build-up. This one definitely does."
Joss Whedon (Buffy the Vampire Slayer, Firefly) has written and directed the comic book film, which will be released on 3D, IMAX and traditional 2D screens.
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> Avengers dwarfs other Marvel films, says special effects chief
> The Avengers releases new teaser pictures