Best Buy said it will boost its Web presence, shrink some larger stores and open more of its smaller US stores to try to win back market share from the likes of Amazon.com and Walmart.

The news came after investors raised concerns about the retailer’s huge overhead costs and oversized stores at a time when many shoppers go online to buy gadgets.

But the plans outlined yesterday did not assuage those concerns.

“We believe the Street wants more. We look at this as a first step that shows us the company is looking at reductions,” Janney analyst David Strasser said.

Best Buy said it wants to double its current $2 billion online business within three to five years.

“The online channel is our greatest growth opportunity,” CEO Brian Dunn said.