US online giant Amazon on Tuesday unveiled an improved version of its market-dominating Kindle e-reader.

The latest Kindle Paperwhite boasts higher contrast, speedier performance, and enhanced touch-screen technology.

"Kindle is the best-selling e-reader in the world for six years running," said Amazon founder and chief executive Jeff Bezos.

"No one is investing on behalf of readers or pushing the boundaries of hardware, software and content for readers like this team."

A version of Paperwhite that connects to the Internet using Wi-Fi will keep the $119 price of its predecessor and being shipping on September 30.

A new Kindle Paperwhite that connects to the Internet using 3G telecom capabilities as well as Wi-Fi will be priced $189 and is expected to begin shipping on November 5.

Tablets designed exclusively for digital books, magazines or newspapers are under pressure from rivals that go beyond reading material to game play, Internet browsing and more.

Amazon backs Kindles with a massive collection of digital works that can be bought as well as a lending library for borrowing digital books.

The Seattle-based online retail titan also announced a MatchBook service that gives Kindle book buyers the option of getting low-cost digital versions of ink-and-paper Kindle editions they have purchased.

Kindle Matchbook will launch in October with 10,000 titles, digital copies of which will range in price from free to $3.