Amazon said the Echo family of devices sold by the “millions,” at a rate nine times greater than last year’s holiday season. It also called this year’s holiday shipping season “record-breaking.”

Share story’s voice-activated artificial-intelligence devices were the stars of what the e-commerce behemoth is calling its “best-ever” holiday season.

Amazon said the Echo family of devices sold by the “millions,” at a rate nine times greater than last year’s holiday season. The Echo is a home speaker through which Amazon’s customers interface with Alexa, a voice-activated software assistant. A smaller version, which connects to speakers, is dubbed the Echo Dot.

“Echo and Echo Dot were the best-selling products across Amazon this year, and we’re thrilled that millions of new customers will be introduced to Alexa as a result,” Jeff Wilke, the head of Amazon’s consumer division, said in a statement.

Wilke acknowledged that the company, despite ramping up production of the Echo line, “still had trouble keeping them in stock.”

Amazon’s comments come amid increased competition in the artificial-intelligence arena from Alphabet’s Google, which recently launched a home speaker that’s similar to the Echo, and other companies. The stakes are high, as experts say voice-activated interfaces point to the future of computing.

Amazon didn’t give out specific numbers, but its disclosure, along with a litany of other shopping facts released Tuesday, hinted at a profitable performance by a retailer that researchers say dominated online shopping during the holiday shopping frenzy.

Analysts expect Amazon to rake in fourth-quarter revenue of $44.71 billion. That’s 25 percent more than in the same quarter last year.

Amazon shares were up 1.6 percent to $772.87 in early afternoon trading Tuesday in New York, outpacing gains in the wider market.

The company said shipping activity, which peaked on Dec. 19, was “record-breaking” during the holiday season.

Amazon said it shipped more than one billion items worldwide under its Prime loyalty program this holiday season, including products shipped by third-party merchants and fulfilled by Amazon. The company also said more people have tried Prime — which costs $99 a year and includes guaranteed shipping, a video streaming service and other perks — than any previous holiday season.

Prime Now, a service that delivers items to consumers in one or two hours, had seen its busiest day ever on Dec. 23, with three times more purchases versus last year.

More than 72 percent of Amazon shoppers used a mobile device during the holiday, and usage of Amazon’s mobile app grew by 56 percent.

Shoppers bought more than 2.5 million watches, 10,451 carats of diamonds, and enough luggage to fill 20 Boeing 747 planes, according to the company.