The publisher of the popular Smurfs' Village game for the iPhone and iPad has added a warning that virtual items such as "Smurfberries" cost real money — as much as $100 US with just two taps on the screen.

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Kelly Rummelhart and her son, Sawyer, 4, who unwittingly racked up nearly $70 in purchases on the Smurf's Village game he played on her iPad, are seen in their home in Gridley, Calif. ((Rich Pedroncelli/Associated Press))

An Associated Press story earlier this month revealed how easy it is for kids to buy such virtual items and have them billed to their parents without their knowledge. Like many other free games, Smurfs' Village makes money by selling the virtual goods to advance play.

Capcom Entertainment Inc. updated the game Sunday. When the game starts up for the first time, a pop-up now warns about the option to purchase Smurfberries and the fact that charges come out of an iTunes account, which gets billed to a credit card.

However, Capcom has also made it easier to make a large purchase of Smurfberries in one go. Previously, the highest two-tap Smurfberries purchase option was a "wheelbarrow" for $59.99. Now it's a "wagon" for $99.99.

Smurf's Village is the third highest grossing game for the iPad. Other top-grossing "free" games for the iPhone and iPad, including Tap Zoo and Bakery Story, have $99.99 in-game purchase options and lack up-front pop-up warnings.

Capcom has said that the big-ticket purchase options are useful to adult "power players" who want to cultivate their Smurf villages. But parents have complained about a loophole in the in-app purchase process that children inadvertently exploit.

Usually, the purchases require the owner of the device to enter his or her iTunes password. But there is no password challenge if the owner has entered the password in the last 15 minutes, for any reason. That means that if a user enters the password for a purchase or a free app upgrade, then hands the phone or iPad over to a child, he or she will not be stopped by a password prompt.

Capcom and other game publishers have no control over the 15-minute password-free period, which is set by Apple.