The chief of the World Health Organization, Lee Jong-wook, has undergone an emergency operation for a blood clot in the brain.

The United Nations agency said in a statement Saturday that Lee suddenly fell ill Saturday afternoon while attending an official function and was rushed to a hospital by ambulance.

Surgeons immediately began an operation to remove a blood clot in his brain, and said he is recovering.

Lee was busy preparing for the World Health Assembly, the annual meeting of the 192 members of the organization opening Monday.

He is the first ethnic Korean to head a U.N. agency.