The firm said that the application has been completely redesigned to allow users to browse sites using a mobile in the same way that they would from a PC.
The most obvious new development is the inclusion of a zoom function, based on the original Opera feature introduced for Nintendo's Wii console.
Opera Mini 'dives' into the page and then snaps to the content so that scrolling is smooth.
Alternatively users can turn on 'fit to width' and view pages in the small screen rendering view in which the structure of the page is changed into a single column, removing the need to scroll horizontally while browsing.
The new version also includes a virtual mouse allowing users to scroll in any direction. The cursor will look for content and links, and snap the view to the area. Scrolling and zooming can also be done using the phone keypad.
Opera also claims that Opera Mini 4 is more than twice as fast as any other mobile browser.
Jon von Tetzchner, chief executive at Opera, said: "The feedback from the beta users will go to make Opera Mini even better and we thank the community for their efforts.
"Opera Mini has succeeded due to the support of the people who have made it the most popular mobile browser available today."
Opera Mini has been downloaded more than 15 million times and used to access more than five billion pages since its worldwide debut in 2006.
Opera Mini 4 beta is available free from the Opera Mini website.
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