posted its ninth straight quarterly profit decline Thursday as it continued to spend heavily on new warehouses and digital content.

Seattle-based Amazon said its first-quarter sales rose 22 percent, a rate of growth matched by its spending, and the company’s profit plunged 37 percent from a year ago.

Although the decline was not as bad as expected, investors sent the stock down in after-hours trading, citing concerns over slower sales growth overseas and a weak second-quarter outlook.

“Amazon is planting lots of gardens, but they haven’t reaped any harvest,” said BGC Partners analyst Colin Gillis, who has a “hold” rating on Amazon stock. “They could pull a Microsoft and take a decade to grow into their valuation.”

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The world’s largest Internet retailer reported $16.07 billion in quarterly sales, about $70 million less than Wall Street expected. Meanwhile, it posted a profit of $82 million, or 18 cents a share, down from $130 million, or 28 cents, a year ago.

Amazon shares closed up $5.92, or 2.2 percent, to $274.70 in Thursday’s regular trading session before the earnings release. The stock initially climbed above $280 after-hours but reversed course and finished the late-trading session at $265.65, a 3.3 percent decline.

Amazon was not immune to economic turmoil overseas, reporting year-over-year sales growth of 16 percent, down from a 21 percent gain three months earlier.

But North American sales were a bright spot, accelerating from 23 percent growth in the fourth quarter to 26 percent last quarter.

Amazon also blew past Wall Street’s profit forecast of 9 cents a share, reversing three straight quarters of missed expectations.

Analyst Scott Tilghman, of B. Riley & Co. in Boston, said Thursday’s stock sell-off is “just a blip on the radar.” He rates Amazon stock a “buy.”

“We’re getting near the point where we could see some pretty significant margin expansion,” Tilghman said. “We’re waiting for the international markets to recover, and we could see some explosive growth there.”

Looking ahead, Amazon expects to post second-quarter sales of between $14.5 billion and $16.2 billion, representing annual growth in the range of 13 to 26 percent.

But the Internet retailer remains cautious in its profit outlook, warning of an operating loss of as much as $340 million or a gain of up to $10 million.

Amazon has been spending heavily on new Kindle devices and licensing agreements for its video-streaming business.

It also is rumored to be developing a new smartphone and television set-top box for video streaming, and its distribution network continues to expand.

Amazon, which ended 2012 with nearly 90 distribution centers, has announced plans for at least three more this year in the U.S.

The company employed 91,300 people worldwide at the end of March, 2,900 more employees than three months earlier.

“They’re going to continue to invest as long as they’re growing between 25 and 30 percent. But it’s a double-edged sword,” said Needham & Co. analyst Kerry Rice, who has a “hold” rating on Amazon stock. “Once growth slows, they’ll probably stop spending. And once growth slows, who’s going to want to invest?”

Wells Fargo analyst Matt Nemer raised the possibility of yet another new endeavor Thursday when he asked Chief Financial Officer Tom Szkutak during a conference call about rumors that AmazonFresh soon will expand.

Amazon has been testing the local grocery-delivery service since 2007, and Nemer sought to confirm reports it’s now adding refrigeration to warehouses beyond Seattle.

“I have nothing to announce,” Szkutak replied. “We’re very pleased with what we’ve seen in the Seattle area. But again, it’s been a test, and we continue to monitor that test very carefully.”

Amy Martinez: 206-464-2923 or On Twitter: @amyemartinez