Internet search firm Google has launched its Froogle price comparison Web site in Britain, expanding the company's e-commerce business and putting it head to head with partners such as Kelkoo. Froogle UK works like the popular Google search engine, but only returns search results from online retailers. Queries for "digital cameras" or "black socks" return a list of products sortable by price or by merchant.

The announcement is the latest expansion from Google following its $1.67 billion initial public offering in August. It said earlier this month it would allow users to search entire books as well as search via text messaging.

Unlike some e-commerce search sites, merchants do not have to pay to be included in Froogle search results. Google makes its money from selling text ads that are linked to search terms and appear alongside search results.

Paris-based Kelkoo -- one of Google's largest advertisers --popularised price-comparison search engines, becoming one of Europe's fastest growing e-commerce sites over the past three years as Europeans caught the online shopping bug, spending billions on everything from holiday packages to MP3 players.

Earlier this year, Yahoo acquired Kelkoo for 475 million euros ($589 million) in an attempt to boost e-commerce revenue and, in particular, tap into Europe's buoyant online retail market.

Froogle's expansion will be decidedly more gradual. The search firm said that, while it was considering expansion into France and Germany, there was no time frame for stepping onto Kelkoo's turf in continental Europe.

"As far as we're concerned, we'd be happy to show Kelkoo's listings," said Cosmos Nicolau, Froogle's engineering director. Nicolau said the company often maintained close relationships with rivals, noting that the Froogle service in the U.S. counts online retailer Amazon.com and Yahoo's shopping service among its retail partners.