Google today introduced brand-image ads for mobile phones, in a bid to extend beyond the computer-based Web market into the emerging market for advertising on phones. The company said it designed mobile images to look like standard graphical display ads for desktop computer webpages, but made them smaller to fit on mobile phone screens.

Mobile image ads are targeted according to the keywords users type into phones to search for information. The ads are priced on a cost-per-click basis, and must link to webpages optimized to work on mobile phones. Google and other Internet companies are increasingly interested in targeting mobile users because they believe the mobile market represents a new opportunity for earning advertising revenue.

"For advertisers, mobile image ads serve as a branding tool and have shown to have good click-through rates," Alexandra Kenin, a product marketing manager.

Mobile image ads are available in 13 national markets: Australia, China, France, Germany, India, Ireland, Italy, Japan, Netherlands, Russia, Spain, the UK, and the U.S.