Leading venture capital firms have invested $18 million in mobile entertainment content provider Thumbplay Inc.

The new funds were raised through a Series E round led by Bain Capital's Brookside Capital Partners and Wasatch Advisors' Cross Creek Capital.

"It's primarily to continue to grow Thumbplay internationally," said Are Traasdahl, founder and CEO of Thumbplay, New York.

"So much of our traffic comes from outside of the United States and currently we're not monetizing that," he said. "We're starting with Europe and Latin America and then we'll go east."

Thumbplay sells more than 80,000 items of mobile entertainment under license, including ringtones, wallpapers, games, voice tones, text-based services and videos.

The extra investment will let the four-year-old company expand its direct-to-consumer product assortment.

Thumbplay has been fairly active in the last few months.

Just in the last quarter the company agreed to integrate its mobile entertainment content catalog into the Web and mobile portals of AOL and MSN Mobile.

The company also struck a similar deal with iLike, a social music discovery services firm.

Also, Thumbplay last month inked a digital distribution deal to add content from Sony BMG Music Entertainment's artists to its catalog (see story).

Mr. Traadahl sees much promise in the mobile content market. He sees a shift from off-deck sales to direct purchases from its WAP site at m.thumbplay.com.

Thumbplay currently attracts between 15 million and 20 million page views to its WAP site. The regular Internet Web site at http://www.thumbplay.com is said to attract between 4 million and 5 million unique users a month, Mr. Traasdahl claimed.

Mobile traffic to m.thumbplay.com is monetized by letting advertisers place banner ads and text-based links as well as running integrated promotions.

Advertisers on Thumbplay's WAP site can target by area code, handset and types of content downloaded.

"We're becoming a larger and larger seller of mobile advertising," Mr. Traasdahl said.

"We're excited about the mobile advertising space," he said. "We see big brands coming in to target this 18-35 audience that are active on their phones and also on the Internet."