Google has launched Image Search Ads, a new format that allows advertisers to display a thumbnail image along with the text in ads on Google Images.

The search engine will feature the image ads on the top of the page.

The new format will be part of AdWords and may be added to, or replace, text-based ads on Google over the long term, said Marissa Mayer, vice-president of search products and user experience at Google, on Tuesday.

The new format will appear only on Google Images for now, but may be extended to other products including its search engine, said Ben Ling, Google's director of search products.

Like the text ads on Google's search results page, the image search ads will be marked as sponsored results.

Google has also revamped its image search with a faster user interface that shows up to 1,000 images on a single page.

The new interface features a pop-up window that will enlarge the highlighted thumbnail.