Google Inc said on Wednesday it has 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.

In a statement on the Silicon Valley company’s Web site, the company said it had designed mobile images to look like standard graphical display ads for desktop computer Web pages, but made them smaller to fit on mobile phone screens.

The company said all 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 Web pages optimized to work on mobile phones.

Only one image ad is displayed on each mobile page, a move to that appears designed to limit clutter on small screens.