Amazon's share price has fallen almost nine percent after the company posted a 57 percent drop in profits for the fourth quarter of 2011.

The drastic fall in profits from $416m (£262) recorded in Q4 of 2010 to just $177m at the end of 2011 is a surprise given that sales of the Kindle range were up by 177 percent year-on-year. Revenue for Q4 was up 35 percent from the year-ago quarter to $17.4bn.

"We are grateful to the millions of customers who purchased the Kindle Fire and Kindle e-reader devices this holiday season, making Kindle our bestselling product across both the US and Europe," said Amazon CEO Jeff Bezos.

Amazon's share price tumbled almost 9.1 percent after the Q4 results were announced, finishing at 176, down 18.44 points at the end of after-hours trading on 31 January.

The ten percent fall may also be blamed on Amazon's conservative expectations for the first quarter of 2012; the company believes that revenue will come in at between $12bn and $13.4bn while net income is thought to range from a $200m loss to a $100m gain.

As always, the company refused to disclose specific sales numbers for the Kindle range, but it did announce that sales of the tablet and ebook readers nearly tripled over the Christmas shipping period and the Kindle Fire remains the bestselling product on

Amazon is believed to sell the Kindle Fire tablet at a loss, instead relying on digital downloads of films, music and applications to make up for lost earning; to that end, the company reports that the number of Instant Video customers has grown 300 percent from Q3 and more than doubled year-on-year.

The full press release from Amazon can be viewed here.