Italian media conglomerate Mediaset Group has sued YouTube for €500 million (US$780 million), alleging the Google video-sharing site illegally hosts thousands of video clips that belong to Mediaset.

The suit, filed in civil court in Rome, names both YouTube and parent company Google. Mediaset operates television stations in Italy and Spain and produces films and TV shows. Its vice chairman, Pier Silvio Berlusconi, is the son of Italian Prime Minister Silvio Berlusconi, who is also a media tycoon.

The company claims that on June 10, there were 4,643 video clips on YouTube, totalling more than 325 hours of material, owned by Mediaset. The company believes that as a result, its three Italian TV stations have lost 315,672 viewing days. The €500 million claim does not include the loss of advertising revenues from the shows.

YouTube is already grappling with a $1 billion copyright lawsuit by U.S. media giant Viacom, which similarly claims its content is offered on YouTube without permission.

YouTube has said its policy is to remove infringing clips if media owners complain.

"Lawsuits like this one threaten the way people legitimately exchange information, news, entertainment, and political and artistic expression over the Internet," YouTube said Wednesday in a statement. "YouTube respects copyright holders and takes copyright issues very seriously. ... We prohibit users from uploading infringing material, and we cooperate with all copyright holders to identify and promptly remove infringing content as soon as we are officially notified."