LOS ANGELES — The fright flick "The Last Exorcism" and the heist thriller "Takers" were in a photo finish for the top spot at the weekend box office, according to studio estimates Sunday.

Lionsgate's "The Last Exorcism" had a thin lead with a $21.3 million debut, closely followed by Sony's "Takers" with a $21 million opening. They were close enough that rankings could change after final numbers are released Monday.

After two weekends in the No. 1 spot, Lionsgate's action romp "The Expendables" slipped to third place with $9.5 million, raising its total to $82 million.

Playing in narrower release, a 3-D special edition of "Avatar" pulled in $4 million, lifting the sci-fi sensation's domestic total to $753.8 million. The new version of the 20th Century Fox blockbuster adds nine minutes of footage.

Both "The Last Exorcism" and "Takers" debuted well above studio expectations, though the openings were modest compared with most big summer debuts.

Overall revenues came in at $115 million, down 8 per cent compared with the same weekend last year, when the horror tale "The Final Destination" opened on top with $27.4 million, according to box-office tracker Hollywood.com.

"We've had two weeks of films being all stacked up very closely to one another, and that's a really tight margin between these two," said Paul Dergarabedian, box-office analyst for Hollywood.com. "But it's sort of a battle in a marketplace that really isn't setting the world on fire."

With summer blockbuster season generally over, late August often is a solid time to release scary movies such as "The Final Destination" and "Halloween II," which opened over the same weekend last year.

"You don't see many low-budget genre films released in June or July or even early August," said David Spitz, head of distribution for Lionsgate. "You don't want to put 'The Last Exorcism' up against 'Inception' or these big blockbuster films."

"The Last Exorcism," about an exorcist trying to cast out a demon from a teenager, cost just $2 million to produce, and Lionsgate bought domestic distribution rights for less than $1 million.

"Takers," which cost a modest $32 million to make, features Matt Dillon, Hayden Christensen, Paul Walker and Idris Elba in a thriller about bank robbers pursued by a tough cop.

Rory Bruer, Sony head of distribution, said he expected "Takers" to remain in second place, slightly behind "The Last Exorcism," once final figures are released Monday. Yet the two movies were pacing Hollywood to a strong finish to the summer season, he said.

"I do think both pictures were pretty terrific for ending summer with," Bruer said. "To have two pictures at $20-plus million at the end of August is a good thing."

The extended version of James Cameron's "Avatar" played in just 812 theatres, compared with 2,874 for "The Last Exorcism" and 2,206 for "Takers."

Besides $4 million domestically, the "Avatar" special edition added $4.3 million overseas. The extra revenue is mere icing for the biggest modern blockbuster, whose initial release took in $2.7 billion worldwide.

"There is no unhappy attached to 'Avatar,' because it's the greatest. It's always done business. It's the biggest picture in history," said Fox distribution executive Bert Livingston. "People bought tickets everywhere this weekend. There's no bad."

Estimated ticket sales for Friday through Sunday at U.S. and Canadian theatres, according to Hollywood.com. Final figures will be released Monday.

1. "The Last Exorcism," $21.3 million.

2. "Takers," $21 million.

3. "The Expendables," $9.5 million.

4. "Eat Pray Love," $7 million.

5. "The Other Guys," $6.6 million.

6. "Vampires Suck," $5.3 million.

7. "Inception," $5.1 million.

8. "Nanny McPhee Returns," $4.74 million

9. "The Switch," $4.7 million.

10. "Piranha 3D," $4.3 million.