SEOUL, Dec 11 (Reuters) - South Korea's agriculture ministry said on Monday it had found a third suspected case of highly pathogenic bird flu at a poultry farm. The case was discovered after culling was completed of all 760,000 poultry near two farms already discovered to have been infected with the deadly H5N1 strain. "We have another another suspected case of highly pathogenic bird flu in a quail farm in North Cholla province," an official said.