Falling sales of videogames and consoles contributed to Amazon.com Inc.'s (AMZN) weaker-than-expected second-quarter North American revenue growth, the Internet retailer's chief financial officer said Thursday.

CFO Tom Szkutak said the decline in sales reflected an industrywide slowdown in videogames and consoles in the quarter. He noted that video sales were being compared with a very strong quarter in 2008, during which a number of the year's top videogame titles hit the market.

The company reported that North American revenue grew 13% to $2.45 billion. That compared with 21% growth in the first quarter of this year. Szkutak said North American media revenue was flat at $1.15 billion, with declines in some categories, particularly videogames and videogame consoles, offset by growth in books.

Szkutak made his comments in a conference call with analysts after the Internet retailer reported second-quarter revenue that fell a fraction short of Wall Street forecasts.

The results sparked a sell-off in Amazon stock, with shares down 6.3% to $87.92 in after-hours trading.

"This is a revenue story, and Amazon's revenue was not perfect enough," said Piper Jaffray analyst Gene Munster.

Chief Executive Jeff Bezos did not participate in the conference call.

-By Scott Morrison, Dow Jones Newswires; 415-765-6118; scott.morrison@dowjones.com