WASHINGTON (AP) — Barack Obama has become the first presidential candidate to buy ad space inside a game.

Eighteen video games, including the extremely popular "Guitar Hero" and "Madden 09," will feature in-game ads from the Obama campaign in the final weeks before the election. The ads — appearing on billboards and other signage — remind players that early voting has begun and plug a campaign Web site that encourages people to register to vote early.

Obama campaign officials said the video game ads target 10 states that allow early voting, including several battlegrounds: Ohio, Iowa, Indiana, Montana, Wisconsin, North Carolina, Nevada, New Mexico, Florida, and Colorado.