Yahoo has announced that its oneSearch will be the main search service on Telefónica's mobile portals in 15 countries in Europe and Latin America.

The new service is expected to reach around 100 million customers worldwide.

Subscribers in the UK and Ireland will receive oneSearch through Telefónica's O2 subsidiary.

Marco Boerries, executive vice president at Yahoo's Connected Life division, said: "Together we can grow usage of mobile internet services and create new revenue streams through mobile advertising."

Customers will also have direct access to photo sharing site Flickr to view and share photos, view friends' pictures and view and create comments.

Yahoo Mail will be integrated into Telefónica's Mail Express platform, allowing users to receive Yahoo Mail messages directly on their mobile phone via MMS.

Mobile advertising is become an increasingly hot topic as more and more people access data services on their mobiles.

"This is not yet mainstream, but I think we are on the cusp of something big, " said Ben Wood, director of telecoms analyst firm CCS Insight.

"Mobile advertising could be a marketer's dream because of the detailed knowledge provided about customers. It makes this segment very attractive to the web giants."

Although exact details were not revealed, the Yahoo/Telefónica deal takes the form of a revenue-sharing agreement under which both parties will split the money made from mobile advertising.