The United Nations says that Sudan has launched a massive vaccination campaign to immunize 2.4 million people against an outbreak of yellow fever in the restive region of Darfur.

The Monday statement from the U.N. Office for the Coordination of Humanitarian Affairs says Khartoum's Health Ministry received an initial shipment of 800,000 doses of vaccine on Friday.

It reported 116 deaths out of 459 suspected cases as of Saturday since the outbreak began in September.

Health experts say Darfur's heavy rainy season this year created additional breeding sites for the disease-carrying mosquitos.

Sudan's government has been battling rebel groups in remote Darfur since 2003. More than 300,000 people have been killed in the conflict, and health care services are not available to many residents as a result of the turmoil.