LOS ANGELES (Reuters) - "Tropic Thunder," a farcical combat movie within a comedy, was the No. 1 film at North American box office for the second week in a row, narrowly beating sorority-themed comedy "House Bunny."

"Tropic Thunder," which stars Robert Downey Jr, Ben Stiller and Jack Black, had an estimated weekend total of $16.1 million at U.S. and Canadian theaters, bringing its total domestic take to $65.7 million, according to box office tracking firm Media by Numbers.

In "Tropic Thunder," Downey, Stiller and Black star as a group of self-absorbed Hollywood actors caught up in a real-life battle with narco-terrorists while filming a war movie in Southeast Asia. The film was directed, co-written and co-produced by Stiller and was distributed by Paramount Pictures, a unit of Viacom Inc.

"House Bunny," from Sony Corp's Columbia Pictures unit, debuted in second place with a weekend take of $15.1 million.

Written by Kirsten Smith and Karen McCullah Lutz of "Legally Blonde" fame, the college comedy stars Anna Farris as a former Playboy playmate who becomes house mother to socially inept sorority sisters.

"Death Race" charged into third with weekend box office of $12.3 million, according Paul Pflug, a spokesman for Universal Pictures, a unit of General Electric Co's NBC Universal.

The film, loosely based on the 1975 movie "Death Race 2000," stars Jason Statham, as a former Nascar champion and ex-con who is framed for his wife's brutal murder and forced by the warden of a notorious prison to compete in a brutal winner-take-all race of weaponized monster cars. Joan Allen stars as the icy prison warden.

The blockbuster Batman sequel "The Dark Knight" slipped to the fourth position with $10.3 million in ticket sales.

"The Dark Knight," a Warner Bros film starring Christian Bale as Batman and the late Heath Ledger as the villainous Joker in his last completed role, has amassed more than $489 million in six weeks of domestic ticket sales and is on its way to becoming one of the highest-grossing films in history.

Warner Bros' animated "Star Wars" movie, "Star Wars: The Clone Wars," rounded out the top five with an estimated $5.7 million in North American ticket sales.