Fighting in Sudan is a devastating setback for the people of the country and "must stop," said the UN Emergency Relief Coordinator on Monday.

"I am deeply concerned by the mounting deaths and injuries, which will only increase further as fighting rages on in urban areas," Undersecretary-General for Humanitarian Affairs Martin Griffiths said.

Although he did not release any statistics on casualties, Griffiths said about one-third of Sudan's population, a staggering 16 million people, needed humanitarian aid even before the fighting erupted.

"Reports that hospitals and water and electrical infrastructure have come under attack are extremely alarming," Griffiths said in a statement issued by the UN Office for the Coordination of Humanitarian Affairs, which he heads.

"The clashes are preventing people, especially in cities, from accessing food, water, education, fuel and other critical services for their families," the UN relief chief said." Health services, already precarious, could be further pushed to the brink."

He said the hostilities aggravated what was already a fragile situation, forcing UN agencies and humanitarian partners to temporarily shut many of the more than 250 programs across Sudan. The impact will be felt immediately, especially in the areas of food security and nutritional support, in a country where some 4 million children and pregnant and lactating women are severely malnourished.

"I am horrified by the deaths of humanitarian workers, including three World Food Programme staff members," Griffiths said. "I am also disturbed by reports of large-scale looting of aid and damage to humanitarian facilities, which will only hamper our efforts to reach those in need. The fighting must stop."

He said the population must be able to safely access essential services, commodities and humanitarian assistance, adding that hospitals and infrastructure for water and electricity supply must be protected.