Amazon: New Kindles Break Sales Records has sold more new generation kindles in the first four weeks of availability than any other generation of Kindle, according to the company.

But keeping to tradition, it still won't reveal any numbers of devices sold.

"Kindle is the best-selling product on for two years running and our new generation Kindles are continuing that momentum," said Steven Kessel, senior vice president of Amazon Kindle, in a statement.

The company said that in the first month of availability, the new Kindle and Kindle 3G sold more untis on and combined than any other product. The Kindles started shipping to customers Wednesday, two days earlier than previously announced.

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According to Google, the new Kindle has a 21 percent smaller body while keeping the same size reading area, 50 percent better contrast of its electronic ink screen, 20 percent faster page turns, is 15 percent lighter at 8.5 ounces, double the storage (up to 3,500 books) and has up to one month of battery life.

Competition for the e-reading market has heated up as sales for all units have increased, particularly from Sony's Reader, Barnes & Noble's Nook, and Apple's iPad, which includes an e-reader. The latter three have expanded their retail presence as a means to gain share on the Kindle, which was released first.

Earlier this month, reports surfaced that the new Kindle ($139 for non-3G and $189 for 3G models) were sold out and on backorder.

Shares of Amazon closed at $126.85 Wednesday, up $2.32 per share or almost 2 percent, after the company released the Kindle sales update.