More than 1,200 children have died in displacement camps across Sudan since May, the UN said on Tuesday.
The deaths are due “to a combination of a suspected measles outbreak and high malnutrition”, said Allen Maina, chief of public health at the UN refugee agency.
Tens of thousands will be “on the brink of death” by the end of the year, he warned.
The UN recorded the deaths, all of children aged under five, at nine camps across the country.
Another 3,100 suspected cases of measles were also reported in the same period, as well as more than 500 suspected cases of cholera in other parts of the country, along with outbreaks of dengue and malaria.
Sudan now has the world's highest number of internally displaced people, Save The Children said.
More than five million have been displaced since war broke out in April, most fleeing the capital Khartoum.
A million people fled to the neighbouring countries of Egypt, Chad and South Sudan after fighting erupted between the Sudanese army and the Rapid Support Forces paramilitary. Many more remain trapped in the country awaiting passports that are locked away in abandoned embassies.
“On the back of a cruel disregard for civilians and the relentless attacks on health and nutrition services, Unicef fears many thousands of newborns will die between now and the end of the year,” James Elder, spokesman for the UN children's agency, told reporters in Geneva.
He pointed out that 333,000 children are due to be born in the country between October and December.
At the same time, nutrition services in the war-ravaged country have been “devastated”, he said.
“Every month 55,000 children require treatment for the most lethal form of malnutrition, and yet in Khartoum less than one in 50 nutrition centres is functional. In West Darfur it's one in 10,” Mr Elder said.
Cases of malnutrition have risen by 300 per cent in Al Jazirah state, according to a recent update from the UN's Office for the Co-ordination of Humanitarian Affairs.
“At least 435 children have reportedly been killed during the conflict and a further 500 have died from hunger – although the exact toll is likely much higher,” it said.
Displaced families have been left in a “dire” situation amid funding shortfalls, reduced food production and severe drought, it added.
Unicef also said it sorely lacked funds, noting that it had received just a quarter of the $838 million it had requested to help 10 million children in Sudan.
AFP contributed to this report
