Amazon.com posted quarterly results Thursday that fell short of expectations and handed in a weak revenue outlook.
Additionally, Amazon said during its conference call it may increase the cost of its popular Amazon Prime subscription by $20 to $40 due to higher fuel and other shipping costs.
There were no immediate details on when or how Amazon would make the decision during the call. The company did not disclose the exact number of Prime customers.
"We have added massive selection and digital content to the service—Kindle owners lending library, Prime instant video," according to CFO Thomas Szkutak during the call. "It's great value for customers. We see customers love it and we will continue to make that better over time."
In December, Amazon said that its Prime service had a "record-setting holiday season." According to the company, more than 1 million people signed up in the third week of December alone. Prime members get free two-day shipping on eligible items, free streaming of 150,000-plus movies and TV episodes, and free e-book borrowing from a library of more than 475,000 titles.
The world's largest Internet retailer posted earnings of 51 cents a share on sales of $25.59 billion, versus expectations for 66 cents a share on sales of $26.06 billion, according to a consensus estimate from Thomson Reuters.
In addition, the company posted current-quarter sales guidance of between $18.2 billion and $19.9 billion, missing expectations for $19.67 billion.
The company said international sales gained just 13 percent, lower than Wall Street forecasts for around 14 percent to 15 percent.
Shares initially shed nearly 10 percent in extended-hours trading before gradually recovering from lows. The stock rallied nearly 5 percent during the regular session Thursday. (Click here to get the latest quotes.)
The stock has had a stellar run since the lows of 2009, with shares surging close to the $400 mark by the end of 2013.
"It's a good time to be an Amazon customer. You can now read your Kindle gate-to-gate, get instant on-device tech support via our revolutionary Mayday button, and have packages delivered to your door even on Sundays," said CEO Jeff Bezos in the company's press release. "In just the last weeks, Forrester, YouGov, and ForeSee have all ranked Amazon #1—and we believe we're just scratching the surface of what world-class customer service can be."
Earlier this week, the Wall Street Journal reported that Amazon plans to move into the mobile payments business, offering brick-and-mortar retailers a checkout system that uses Kindle tables as soon as this summer, citing sources.
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Recently, Amazon also expanded its grocery delivery service to two new U.S. cities, introduced Sunday package delivery with the Postal Service and reached agreements to build warehouses in several states.
—By CNBC's JeeYeon Park. Follow her on Twitter @JeeYeonParkCNBC