An advertisement featuring a bikini-clad Beyonce Knowles has angered locals in Las Vegas, after they complained the billboard was "obscene".The R&B beauty appears on an advert for the city's KWNZ radio station, but residents in Sin City are petitioning to have the raunchy image taken down.Resident Pamela Keeney says: "It's obscene. I have my two little grandkids coming over here, and they don't need to be seeing that. You can change the channel on the TV but you can't change that."However, KWNZ has stood by the billboard and has received the backing of city spokesman Chris GoodScott Seidenstricker, manager of KWNZ, says: "The billboards were taken from publicity shots and this is the way those people perform. So to show them in a jogging suit probably wouldn't be the right thing."Good adds: "It complies with all the locational criteria that are set out in our (advertising) code (of conduct)."