The number of cases reported up to June in 17 of Sudan's 18 states is more than four times the figure for the whole of last year.
"The outbreak this year is huge and we more than 2,500 confirmed cases of measles" since January, UN interim humanitarian coordinator for Sudan Geert Cappalaere told AFP.
"Measles is something we see in Sudan every year, but we see yearly not more than 500 or 600 cases over the whole year," he said.
The government, with support from the UN children's fund UNICEF and other aid agencies, has launched a campaign to vaccinate 7.9 million children under 15 against the disease.
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Some 72 percent of the 2,511 confirmed cases of the disease are children in that age group.
The campaign started in the first week of June, targeting parts of eastern Sudan and Khartoum state.
The second stage of the campaign, which was started today , will target the western Darfur region, which is home to 2.5 million people who have been displaced by fighting between the government and rebels since 2003.
Cappalaere said this year's outbreak was likely due to the fact that not enough children had been vaccinated in previous inoculation drives.