LOS ANGELES -- Ben Stiller comedy "Tropic Thunder" dethroned Batman sequel "The Dark Knight" from the top spot at North American box offices this weekend, entertainment industry estimates showed Sunday.

Stiller's movie-within-a-movie about a group of actors shooting a war movie in the middle of a real-life conflict zone scooped $26 million on its opening weekend, according to box-office tracker Exhibitor Relations.

The impressive opening haul gave the film -- which also stars Robert Downey Jr and Jack Black -- five-day earnings of just over $37 million.

It came after the film's premiere saw protests from disability activists who lambasted Stiller for repeated use of the word "retard" in the script. Stiller has defended the movie, insisting that it is a satire on Hollywood.

The success of "Tropic Thunder" knocked "The Dark Knight" off of top spot after four weeks of dominance.

But "The Dark Knight," which features Christian Bale as the caped crusader and Heath Ledger as his arch-villain Joker, earned another $16.8 million which was enough to take the film past "Star Wars" as the second highest-grossing movie of all time after 1997's "Titanic."

"The Dark Knight" has now raked in a cool $471.5 million since opening in mid-July, but is still way off "Titanic's" mammoth haul of $601 million.

Ironically, the milestone came on the same weekend as the animated "Star Wars: The Clone Wars" arrived in US theatres. The latest offering from George Lucas's money-spinning franchise opened in third with $15.5 million.

The latest Hollywood remake of a cult Asian horror film "Mirrors", starring Kiefer Sutherland, was in fourth spot with $11.1 million.

In fifth place was the marijuana comedy "Pineapple Express", starring Seth Rogen and James Franco, which earned $10 million.

Critically panned action-adventure "The Mummy: Tomb of the Dragon Emperor" was sixth with $8.6 million, ahead of Abba musical remake "Mamma Mia!", with $6.5 million.

Rounding out the top 10 were "The Sisterhood of the Traveling Pants 2" with $5.93 million, ahead of comedy "Step Brothers" with $5 million.

Woody Allen's latest film, romantic comedy "Vicky Cristina Barcelona" was 10th with $3.7 million although it was screened in fewer than 700 theaters nationwide.