Google has started supporting a “click-to-call” feature in AdWords on mobile smartphones.

The feature lets a phone user click on a phone number in an advertisement to automatically place a call to the advertiser.

The ads and phone numbers displayed are based on the caller’s location, so if a user searches for a chain store, the ad will automatically display the closest location, said Surojit Chatterjee, a product manager in Google’s Mobile Ads Team, in a blog post.

For an advertiser, the cost of a click-to-call is the same as the cost of a click to visit its Web site. Advertisers will be able to see how many calls originate from the ads in the campaign summary in their AdWords account.

In a beta test, Google said advertisers using the feature saw a 5 percent to 30 percent increase in click-through rates on their ads.

This isn’t the first time Google is offering click-to-call services. Advertisers can also set up click-to-call AdWords campaigns for WAP (Wireless Application Protocol) phones, lower-end devices that support more limited Web use.

The new click-to-call ads can be displayed on phones that have full Internet browsers.

For a while Google also offered click-to-call in its Maps service, but discontinued that in 2007.

Google is among a handful of Internet players vying for leadership in the potentially significant mobile advertising market. It recently bought AdMob, a mobile display-ad technology provider. Earlier this month, Apple bought mobile ad company Quattro. Microsoft and Yahoo are also working to secure footholds in the market.

By Nancy Gohring