MINNEAPOLIS — Best Buy said Thursday it had disappointing sales during the holiday shopping season, raising concerns about the consumer electronic retailer’s ability to turn around its business.

Shares tumbled nearly 29 percent on the news, showing that investors are increasingly worried about Best Buy’s future. Best Buy’s stock price had more than quadrupled last year, but had been down 7 percent since the beginning of this year.

The holiday season, which runs from November through December, is a critical period for retailers because it can account for up to 40 percent of their annual revenue. But this past season was marked by weak consumer spending and heavy sales promotions by retailers.

Best Buy was struggling even before the holiday season because of increased competition from online stores, notably Amazon.com, and discounters like Wal-Mart. But under CEO Hubert Joly, Best Buy started a turnaround strategy that included revamping merchandise, training employees and cutting costs.

Best Buy went into the holiday season saying that it was unafraid of so-called “showrooming,” when consumers check out items in stores and then purchase them for cheaper online. It also said it would match prices of all retailers, including cheaper online rivals, but that policy ultimately led to an unexpected sales decline.

Best Buy CEO, Hubert Joly, also said that there was a lot of competition on price during the holidays and an “intensely promotional” environment. He added that Best Buy’s business was also hurt by supply constraints for key products, a drop in customer traffic and a disappointing mobile phone market.

Additionally, Joly said there was an overall decline in the consumer electronics market that no one was expecting. Indeed, according to research firm NPD Group, consumer electronics sales fell 2.4 percent to $22.9 billion during the 9-week holiday period.

As a result, total revenue for the nine-week period that ended on Jan. 4 slipped 3 percent to $11.45 billion from $11.75 billion. Domestic revenue declined to $9.75 billion from $9.91 billion, while international revenue fell to $1.7 billion from $1.85 billion.

Meanwhile, sales at stores open at least a year — a key indicator of a retailer’s health — fell 0.8 percent. But that was better than the 1.4 percent decline in the prior-year period.

“Best Buy is in a much better position than it was a year ago,” said Morningstar analyst R.J. Hottovy. “In my mind, the shares now more accurately reflect very competitive retail environment that will be present in the years to come.”

Joly said Best Buy’s holiday performance renews the sense of urgency around the company’s transformation. He said that key priorities heading into fiscal 2015 will include: lowering costs faster and more deeply; growing its online business at a quicker pace; continuing to improve the customer experience; improving marketing efforts and growing its Geek Squad services business.

Joly also said there were no specific plans to close stores, but added that “we have always said on an ongoing basis that we are looking at the store footprint and we continue to review it.”

Shares of the Minneapolis company declined $10.74, or 28.6 percent, to close at $26.83 after sinking more than 30 percent earlier.