Stellan Skarsgard plays Father Merrin in Exorcist: The Beginning

Exorcist: The Beginning beat another new entry, comedy Without a Paddle, which was second with $13.7m (�7.5m).

The Exorcist film had three directors, was totally reshot because it was too tame at first, and final director Renny Harlin was injured by a car on set.

Last week's top film Alien vs Predator dropped to fourth with $12.5m (�6.8m).

In third place was The Princess Diaries 2: Royal Engagement, while cult shark thriller Open Water jumped 12 places to number five.

If you're looking for groundbreaking badness, you needn't look much further than the new Exorcist prequel Boston Globe review

King Arthur remained in the number one spot in box offices outside the US last weekend - adding $12.5m (�6.9m) to its international takings of $92m (�50.6m).

Paul Dergarabedian of box-office tracker Exhibitor Relations said of the new Exorcist film: "You can always count on horror films to do well.

"There's just this built-in audience base that loves this genre."

But critics, who were not given advance screenings, have not been kind. "Satan save us from any more Exorcist sequels," was the Toronto Star's headline.

The Boston Globe wrote: "If you're looking for groundbreaking badness, you needn't look much further than the new Exorcist prequel, which is one interminably grisly waste."

"After a well-paced first two acts, Exorcist: The Beginning eventually collapses under its enormous weight," wrote the San Francisco Chronicle.

US AND CANADA BOX OFFICE 1. Exorcist: The Beginning, $18.2m 2. Without a Paddle, $13.7m 3. Princess Diaries 2: Royal Engagement, $13.2m 4. Alien vs Predator, $12.5m 5. Open Water, $11.75m Source: Exhibitor Relations Co. Figures: Friday-Sunday

The Hollywood Reporter said: "The scariest thing about this film is how desperate the makers are to earn a scream."

Exorcist: The Beginning was first announced in 2001, with director John Frankenheimer and actor Liam Neeson on board.

But Frankenheimer pulled out a month before he died in 2002, with Raging Bull and Taxi Driver screenwriter Paul Schrader taking over.

Swedish actor Stellan Skarsgard replaced Neeson in the lead role of Father Merrin - but film studio Morgan Creek did not think the finished movie was scary enough.

So it replaced Schrader with Harlin and changed most of the cast, but Skarsgard stayed in his role.

Then the whole film was shot again.

'Darker'

"The first one we did was more of a psychological thriller, basically about a man in crisis," Skarsgard said.

"For the Renny Harlin movie I changed the performance, I even changed the make-up.

"I think I went much darker in the Schrader version."

During filming, Harlin was hit by a car in Rome and spent the rest of the shoot on crutches with bones in one leg held together by 14 metal pins.

Harlin said he took talk of an Exorcist curse seriously. "It's not very funny, if you think about it," he said. "I believe in it."

Exorcist: The Beginning is the fourth Exorcist movie, with two sequels released in 1977 and 1990.