The movie, from Walt Disney Co. unit Marvel Studios, staked its claim to the second-highest midnight debut for a non-sequel film, coming in about $1 million shy of the March 2012 total for "The Hunger Games" at $19.74 million, according to industry tracker Hollywood.com.

"Avengers," in which Iron Man, Thor, Captain America and Black Widow, among others, ban together to combat evil on earth, landed at No. 8 on the list of all-time best midnight openings behind several "Harry Potter" and "Twilight" franchise films.

The best midnight debut belongs to "Harry Potter and the Deathly Hallows - Part 2," the final movie in that series that conjured up $43.5 million in its midnight debut last year.

"The Avengers" debut kicks off four months of movie going filled with effects-laden flicks, adventure, science-fiction, comedy and big-name Hollywood stars meant to lure mostly younger audiences that are out of school for the summer. The season can bring in as much as 40 percent of annual movie ticket sales in the United States and Canada.

Already, "Avengers" has leveraged its superhero status to a massive box office in international markets after just nine days in theaters. As of Friday morning, ticket sales reached $304 million, Disney said, surpassing total overseas receipts for "Captain America," the first "Iron Man" and "Thor."

That strong international demand has helped boost forecasts for opening weekend U.S. and Canadian sales. The movie could challenge this year's debut weekend record of $152.5 million set by teen survival drama "Hunger Games," box office analysts said.

The international fervor has "created a lot of excitement on this side of the pond. That's increased my expectations" for the domestic opening, said Paul Dergarabedian, president of the box office division of Hollywood.com, who predicts domestic (U.S. and Canadian) ticket sales of $150 million-plus from Friday through Sunday.

Phil Contrino, editor of Boxoffice.com, thinks "Avengers" has a shot at breaking the all-time opening record set by last summer's "Harry Potter and the Deathly Hallows - Part 2" with $169.2 million. Higher-priced 3D tickets will help lift the total, he said. "I think this is a movie people will seek out in 3D," said Contrino. He is forecasting a domestic debut of around $170 million.

(Reporting By Bob Tourtellotte; Editing by Doina Chiacu)

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