LONDON — Sudoku, a simple yet baffling Japanese number puzzle, is sweeping Britain faster than a news flash about Prince William's girlfriend Kate Middleton.

And now it's getting a foothold in the United States.

Sudoku is like a crossword puzzle that uses numbers instead of words. It's a grid of 81 squares, divided into nine blocks of nine squares each.

Some of the squares contain a digit. The goal is to fill in the empty squares so that the digits 1 through 9 appear just once in every row, column and individual block.

It sounds easy, but "it can make your brain ache, your pulse race, and your knuckles whiten as you grip your pen in exasperation or, finally, ecstasy," said Richard Pendlebury, a writer for the Daily Mail.

His is one of at least four national newspapers publishing daily Sudoku puzzles. Web sites devoted to the craze abound, and a version for cell phones is on the way.

Sudoku Selection, the first monthly magazine devoted to the craze, was launched here this week, and several Sudoku books are on the market.

Well-known British TV presenter Carol Vorderman told the Independent newspaper that she's so hooked she has competitions with friends to see who finishes first.

"Once I've put the kids to bed, all I want to do is get down to a number puzzle," she said. "I've become a bit of a saddo."

Sudoku can be roughly translated as "the number that is single." Its actual origins are murky. The 18th-century Swiss mathematician Leonhard Euler developed something very similar, which he called Latin squares.

Wayne Gould, a retired judge from New Zealand, discovered the game in Japan in 1997 and has spent the past few years developing a computer program that devises fresh Sudoku puzzles. He introduced the game to Britain in the Times newspaper last fall, and sells his program on www.sudoku.com.

Now Gould and others see signs that the craze may hop the Atlantic.

After the New York Post began publishing Sudoku puzzles in April, the paper said it was inundated with appeals from readers to publish harder ones. More U.S. papers are coming on board all the time.

"Wherever it has appeared in the United States it has been a hit with readers," Gould said. "Addiction, whether good or bad, tends to ignore national boundaries."

Nick Jordan, who runs a British Web log with a section on Sudoku, said he's already receiving up to 300 visits a day from American puzzle fans, a high rate for his site.

"I suspect there is indeed a growing interest in the game there," he said.

Gould said that the release of a book on Sudoku in the United States within the next few months by a division of the Penguin Group will help spread interest.

John Brazier of www.sudoku-solver.com said he believes the Sudoku craze will go worldwide simply because it offers something for everyone.

"Unlike crosswords, Sudoku puzzles are culture-neutral," he said. "They are attractive to all people."