The Director-General of the World Health Organisation, Dr. Lee Jong-wook of South Korea, has died suddenly following surgery for a blood clot on the brain.
Lee Jong-wook was 61 and had been the director-general of WHO since 2003.
The announcement was made at the opening session of the agency's annual assembly by Spain's Health Minister Elena Salgado.
The annual assembly was immediately suspended for 30 minutes following the announcement.
The five day meeting aims to discuss the global reaction to the threat of bird flu, whether or not to destroy the world's remaining stocks of smallpox and Taiwan's long-standing bid to win observership.
Lee had undergone an operation on Saturday to remove a blood clot on his brain at the Cantonal Hospital of Geneva after he had been taken ill suddenly in the afternoon.
Mike Leavitt the U.S. Secretary of Health and Human Services has said the death of Dr. Lee Jong-wook is a tragic loss to the World Health Organization and the global health community.
Dr. Lee had devoted his life to public service and to improving the human condition and was regarded as a visionary leader who embraced the spirit of global cooperation and strengthened the role of the WHO in the global community.
Lee had worked for the health agency at country and regional level and at the Geneva headquarters for 23 years and his outstanding leader had made the fight against HIV/AIDS a hallmark of his term of office.