LONDON — The head of the World Health Organization has ordered an internal investigation into allegations the U.N. health agency is rife with racism, sexism and corruption, after a series of anonymous emails were sent to top managers last year.

Three emails addressed to WHO directors complained about “systematic racial discrimination” against African staffers and alleged other instances of wrongdoing, including claims that some of the money intended to fight Ebola in Congo was misspent.

Last month, WHO Director-General Tedros Adhanom Ghebreyesus told staffers he had instructed the head of WHO’s office of internal oversight to look into the charges raised by the emails.

A WHO statement said the agency was “aware” of such allegations and has “zero tolerance for misconduct or discrimination of any kind.”

The statement also said Tedros has “championed openness, transparency and diversity” since he became WHO’s chief.