SAN FRANCISCO -- Superstar Placido Domingo has resigned from the U.S. union that represents opera singers after two investigations found sexual harassment allegations against him to be credible.

The American Guild of Musical Artists said Friday that Domingo also will contribute US$500,000 to sexual harassment eradication programs and a fund that helps opera employees in crisis.

The union and the Los Angeles Opera opened investigations into the singer's conduct after multiple women accused him of sexual harassment and abuse of power in stories published last year by The Associated Press. Domingo had led the Los Angeles company for years before resigning as director in October.