THE surprise winner at the US box office this weekend is Monsters University which, according to early estimates,  has beaten apocalyptic thriller World War Z and Superman reboot Man of Steel to lead the takings.

The Pixar prequel to Monsters Inc took $82 million in ticket sales, beating World War Z's $66 million and Man of Steel's $41.2 million.

Monsters University, featuring the voices of Billy Crystal and John Goodman, is Pixar's 14th consecutive film to head the box office at its weekend debut.

Dave Hollis, executive vice president of distribution for Walt Disney Studios, said: "It definitely exceeded our expectations. The first film was so beloved and set such a high bar so we're ecstatic."

Despite coming second at the box office to Monsters University, World War Z, starring Brad Pitt, achieved better ticket sales than analysts predicted.

World War Z studios Paramount Pictures predicted sales in the $40 million region given the competition from Monsters University and Man of Steel.

But results exceeded targets by over $20 million.

Don Harris, president of distribution for Paramount, said: "I don't think there's a person on the planet who thought this would open at $66 million."

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In terms of Paramount's recent blockbusters, he added, it ranked behind Iron Man and Transformers as "the third largest potential franchise opening in the history of the company".

Warner Bros' Man of Steel, starring British actor Henry Cavill, came third in the US box office weekend sales, bringing its North America revenue to more than $210 million .

This is the End, an apocalyptic comedy written by Seth Rogen and Evan Goldberg, came fourth with takings of $13 million.

Now You See Me, a thriller starring Jesse Eisenberg, took $7.87 million to secure fifth place.