Amazon is closing all its U.S. pop-up stores, with the retailing giant confirming plans to close 87 kiosks in malls and Whole Food and Kohl's stores around the country.

"After much review, we came to the decision to discontinue our pop-up kiosk program," an Amazon spokesperson told CBS MoneyWatch by email.

Amazon is instead expanding its bookstores and so-called 4-star stores offering highly rated items, and will open additional locations of both brands this year, the spokesperson added.

Located in shopping malls and Kohl's stores and Amazon's Whole Foods stores in 21 states, the pop-ups are expected to be shuttered by the end of April, some of their employees told the Wall Street Journal.

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Kohl's CEO Michelle Gass told analysts in a conference call Tuesday that the retailer would sell Amazon-made electronics after the 30 Amazon kiosks it houses in its retail stores close.

The latest development doesn't mean Amazon is pulling back from the brick-and-mortar retail business. The online retailer also operates Go-branded convenience stores without cashiers, and two years ago purchased Whole Foods and its more than 460 stores.