A yellow fever outbreak has killed nearly 100 people over the last seven weeks in Sudan's Darfur, the World Health Organization said, a region where fighting has undermined access to healthcare.

The mosquito-borne disease has spread throughout the remote western territory, but the reported cases have been concentrated in central Darfur, the WHO and Sudan's health ministry said in a joint statement.

Darfur has been plagued by conflict since rebels took up arms in 2003, complaining that the government had neglected the region and locked its non-Arab minorities out of power.

Healthcare is provided almost entirely by aid agencies in some parts of Darfur.

The statement said 329 suspected yellow fever cases and 97 deaths had been reported since the last week of September. The outbreak had hit the regional capitals of El Geneina and Nyala.

There is no effective treatment for the hemorrhagic fever, but there is a vaccine. Some 3.6 million people would be vaccinated in the affected areas, the statement said. It did not say how long the program would take.

Nearly half the yellow fever cases were in people between the ages of 15 and 30, it said, and about a quarter were children aged five to 15.

Hundreds of thousands of people may have died in Darfur's conflict, the United Nations and human rights groups have estimated. The government has put the death toll at 10,000.

The International Criminal Court has issued an arrest warrant for Sudan's President Omar Hassan al-Bashir on charges of war crimes in the region. He denies the allegations.