UPDATE 2-'Saw IV' butchers competition at box office

(Includes foreign rankings for "Saw IV" in paragraph 8)

By Dean Goodman

LOS ANGELES, Oct 28 (Reuters) - If it's Halloween, it must be time for the "Saw" horror franchise to scare up the top spot at the North American box office.

"Saw IV," the latest installment in the annual series about a sadistic serial killer named Jigsaw, sold about $32.1 million in tickets during the weekend, according to studio estimates issued on Sunday.

Opening at No. 2 was the Steve Carell comedy "Dan in Real Life," with $12.1 million. Last weekend's champion, the vampire thriller "30 Days of Night," fell to No. 3 with $6.7 million.

"Saw IV," opened about $1.5 million lower than its predecessor this time last year, breaking a pattern that had seen each new installment open more strongly than the previous one. But most franchises are usually running on fumes by the time the fourth iteration hits the screens, a fate that evidently has yet to befall "Saw."

Exit polling indicated that 89 percent of the film's audience had seen all three previous entries, a sign of "tremendous brand loyalty," said Steve Rothenberg, president of distribution at Lionsgate, which released the film.

Additionally, 68 percent were aged under 25, about the same as with "Saw III," Rothenberg said. He attributed the films' success to the "creativity of the traps" that portend a grisly demise for their victims.

The top grosser in the series is 2005's "Saw II," which finished with $87 million after a $31.7 million start. "Saw III" took in $80.2 million overall.