SINGAPORE -- Frantic to get limited-edition Hello Kitty toys, customers pressed against the glass door of a McDonald's and shattered it, leaving seven people injured, the company said Friday.

The restaurant staff gave victims first aid Thursday after the door broke under the pressure of the crowd, the company said in a statement. Three customers were hospitalized and later discharged.The sale of Hello Kitty characters -- round-faced kittens dressed in wedding outfits -- has attracted huge crowds at McDonald's outlets in Singapore since the toys were released at the beginning of the month.

For every purchase of an Extra Value Meal, customers can buy a pair of Hello Kitty characters for about $2.70. A different pair is being sold each week over a six-week period.

The huge response has led McDonald's to call in police to help deal with the flow of people at some of its more crowded outlets.

"We would like to appeal to all customers to keep calm and follow the directions of our staff on the scene," McDonald's director of marketing Fanny Lai said.

Since Hello Kitty's creation 25 years ago, the feline with the bow on her ear has boomed across Asia and the United States, bringing in hundreds of billions of dollars for her creator, Japan's Sanrio Co.