The UN's top official in Sudan on Tuesday called for immediate access to southern Darfur where thousands of civilians have been affected by rebel-government fighting but relief teams have been denied access for security reasons.
Ali Al-Za'tari, citing government figures, said about 36,000 people have gathered around the bases of international peacekeepers in Muhagiriya and Labado, some 100 kilometres (62 miles) east of the South Darfur state capital Nyala.
"Reports received by the United Nations indicate an outbreak of diarrhoea among children requiring urgent and immediate assistance," Za'tari said, expressing "serious concern" for civilians in the area.
He said aid workers need access right away to assess the people's condition and provide relief supplies.
Za'tari urged the government and rebels of the Sudan Liberation Army's Minni Minnawi faction "to uphold their humanitarian responsibilities to protect all civilian populations."
He stressed civilians wanting to leave the area must be allowed safe passage.
On Monday a UN official said "authorities deemed it too insecure" for aid agencies to enter Muhagiriya and Labado.