Amazon, in the latest salvo in the electronic book reader war, unveiled a new version of its large-screen Kindle with a slashed price.

The new Kindle DX, which features a 24.6-centimetre screen, costs $379, down from $489.

Apple's cheapest iPad, the Kindle's chief rival, costs $499 and features a colour e-reader compared with the black-and-white Kindle, which is devoted exclusively to digital books.

The Kindle DX price cut comes just days after Amazon lowered the price of the basic Kindle, which features 15.2-centimetre screen, to $189 from $259.

US bookstore giant Barnes & Noble offers a version of its e-reader, the Nook, with 3G and Wi-Fi connectivity for $199 and a Wi-Fi-only Nook for $149.

Amazon said the new Kindle DX offers an electronic ink display with better contrast, providing clearer text and sharper images.

"With 50 per cent better contrast and darker fonts, you'll find it easier than ever to read wherever you happen to be," Kindle senior vice president Steve Kessel said in a statement.

The new Kindle DX ships on Wednesday.

Apple has sold more than three million iPads since the device went on sale in early April.

Amazon touts the Kindle as the top-selling item at the online retailer, but does not release sales figures.

Amazon also said that the Kindle Store now offers more than 620,000 books, including 108 of the 111 New York Times bestsellers, and over 200,000 books have been added to the US Kindle Store in the past six months.

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