Superhero sequel "Avengers: Age of Ultron" scored the second biggest North American box office opening of all-time but failed to eclipse the record set by its 2012 predecessor, industry estimates showed Sunday.

The latest big-screen offering based on the iconic Marvel comics characters raked in a staggering $187.7 million in its first weekend, figures from box office tracker Exhibitor Relations showed.

However it fell short of surpassing the record $207.4 million opening posted by "The Avengers" three years ago.

Analysts said Saturday's crowded schedule of sports events -- which included the Floyd Mayweather-Manny Pacquiao superfight, the Kentucky Derby and NBA playoffs -- could have contributed to the shortfall.

Exhibitor Relations analyst Jeff Bock said the latest "Avengers" film also lacked the novelty of the first movie, which united beloved characters such as Captain America, The Hulk, Thor, Iron Man in one movie for the first time.

"It was always going to be tough to top the first movie," Bock told AFP. "The first film had the novelty of all these superheroes together in one film which we hadn't seen before. So 'Ultron' didn't have that advantage."

The latest "Avengers" film, which sees Chris Evans (Captain America), Robert Downey Jr (Iron Man), Mark Ruffalo (The Hulk), Chris Hemsworth (Thor), Scarlett Johansson (Black Widow) and Jeremy Renner (Hawkeye) return, has also received a cooler critical welcome than the first film.

The Rotten Tomatoes review aggregator website gave the film a 75 percent rating compared to the 92 percent ranking enjoyed by its predecessor.

The latest film sees the superhero team battling to save the earth from destruction by the villainous robot Ultron, voiced by James Spader.

The Avengers juggernaut flattened every other film at the box office this weekend, with no other movie managing to make it past the $10 million barrier.

Second place went to fantasy drama "The Age of Adaline" starring Blake Lively as a woman in the 1920s who mysteriously stops aging after being involved in a car accident. The film took $6.3 million.

Third place went to the blockbuster car racing action movie "Furious 7", which added another $6.1 million. The film has grossed $1.4 billion worldwide.

Fourth spot went to "Paul Blart: Mall Cop 2" with $5.5 million, just ahead of "Home", an animated children's film about an unpopular space alien forced to flee his own kind, with $3.3 million.

Disney's live action version of "Cinderella" was next with $2.4 million, ahead of acclaimed science fiction thriller "Ex Machina" in seventh with $2.2 million.

Social media horror flick "Unfriended," was in eighth place with $2 million, with romance novel adaptation "The Longest Ride" starring Scott Eastwood, ninth with $1.7 million.

Rounding out the top 10 was "Woman in Gold," the true story of a Holocaust survivor trying to get back her Nazi-looted artwork from Austria. It earned just under $1.7 million.