The head of the World Health Organization, Lee Jong-wook, died in Geneva Monday afternoon after undergoing emergency surgery for a blood clot in his brain. He was 61.

The organization informed South Korea of Lee's demise and will make an official announcement on the cause of death soon.

The first South Korean to head a U.N. agency, Lee on Saturday was rushed to Cantonal Hospital in Geneva while preparing for his organization's annual assembly.

He was an avid proponent of fighting avian influenza since his election to the post in July 2003.