Staples announced Thursday the mass closing of stores in the United States and Canada because of shifts in American shopping habits, the Associated Press reported.

The office-supply company said it will close up to 225 stores in the United States and Canada - more than 10 percent of its North American outlets - because nearly half of its sales are generated online. They are also aiming to cut costs and become more efficient, the AP reported.

"This is essential," Staples Chairman and CEO Ron Sargent told analysts, according to the AP. "Our customers are using less office supplies, shopping less often in our stores and more online, and the focus on value has made the marketplace even more competitive."

The mass closing will save Staples about $500 million by 2015.

Bill Martin, co-founder of ShopperTrak, which tracks data at about 40,000 U.S. stores, told the AP that shoppers make fewer store visits because they are buying and window shopping online. That is part of the reasons the number of stores is contracting even though overall sales are growing, albeit at a slower pace.

"I think it's pretty clear that the consumer is evolving and might be evolving at a little faster pace than retail," he said, noting that shoppers can now use smartphones to compare prices during a store visit.

Sargent added that his company's stores have fallen short on expectations in the past three years; Shares of Staples fell as much as 17 percent "after the company also reported weaker-than-expected fourth-quarter results and forecast a profit for the current quarter that fell far below analysts' estimates.

Staples has become the second major chain to announce the mass closing of stores this week. Two days ago, RadioShack announced plans to close up to 1,100 stores, about a fifth of its U.S. locations.

The office-supply company has 1,846 stores in North America and Canada, the vast majority in the United States.