Amazon second quarter revenues jumped 22 percent annually to $15.7 billion from $12.8 billion. But despite the sales boost, the online retailer posted net income losses of $7 million.

In a press release yesterday, Amazon put the focus on a 41 percent jump in operating cash flow, to $4.5 billion for the 12 trailing months compared to $3.2 billion at the same time last year. But free cash flow dropped 76 percent annually to $265 million after figuring in capital expenditures like 2012 purchases of new corporate office space and property totaling $1.4 billion.

Behind the mixed financial results, CEO Jeff Bezos played up the success Amazon has seen with its Kindle line of tablets.

“This past quarter, our top 10 selling items worldwide were all digital products – Kindles, Kindle Fire HDs, accessories and digital content,” Bezos said.

Amazon added that the Kindle Fire HD and the 8.9-inch version of it are now available to customers in more than 170 countries and territories globally.

In the Q&A portion of the earnings call, CFO Tom Szkutak pointed to the Kindle Fire HD and Paper White being released in China as signs of advancement in the global market for Amazon’s tablet.

“But again, it’s very early,” Szkutak said, seeming cautiously optimistic while adding he is “very encouraged by the opportunity that we have there for customers and our ability to try to capitalize on that from a digital content standpoint.”

In its third quarter guidance, Amazon saw third quarter sales rising 12 to 24 percent annually.

A report earlier this year from the Wall Street Journal suggested that Amazon was at work on two smartphones and an audio streaming device, all for possible release in 2013.

Following the quarterly report, Amazon’s stocks have dipped about one percent in pre-market trading.