Cast member Malin Akerman attends the premiere of the movie Watchmen at the Grauman's Chinese theatre in Hollywood, California March 2, 2009. The movie opens in the U.S. March 6. (Xinhua/Reuters Photo)

 Warner Bros.' sci-fi action Watchmen became the superhero at the box office this weekend in North America, with the biggest opening so far in 2009, but the highly-pitched film fell short in surpassing director Zack Snyder's previous blockbuster 300.

Watchman, a film adaptation of a famous graphic novel about a team of flawed heroes, opened with an estimated 55.7 million dollars in the United States and Canada, Los Angeles-based research firm Media By Numbers said on Sunday.

But Snyder's latest bloody and special-effects-laden film failed to live up to many analysts' expectations to surpass 300,his last film setting the record for best March opening in 2007, when it had a 71-million-dollar opening weekend.

Watchman is set in New York in an alternate-reality 1985, when Richard Nixon is in his fourth term as U.S. president, and the United States and the Soviet Union make peace to face a nuclear threat to the humankind.

Officially opened on Friday in a total of 3,611 theaters in North America, the film is the widest release ever for an R-rated film, after it played more than 1,600 locations starting Thursday midnight.

Finishing in second place over the weekend is Lionsgate comedy Tyler Perry's Madea Goes To Jail with 8.8 million dollars in its third weekend of release, followed by 20th Century Fox's thriller Take with 7.5 million dollars.

Oscar-winning independent film Slumdog Millionaire was in fourth with 6.9 million dollars and Sony Pictures' comedy Mall Cop in fifth with 4.2 million dollars.

(Xinhua News Agency March 9, 2009)