A charity has launched a £3 million appeal to help hundreds of thousands of children returning to southern Sudan for next month's vote on independence.
Save the Children warned that about 400,000 children are facing months of hardship and hunger, with many forced to live on the streets or in cramped temporary shelters without enough food or clean water.
More than 77,000 people have returned since the beginning of November and the UN are expecting 800,000.
Many of the returnees are staying with extended families, with reports of up to 58 people lodged in a single home.
Southern Sudan already has a severe shortage of health clinics, hospitals and schools.
Steve Morgan, Save the Children's country director, said: "Southern Sudanese children are among the poorest in the world. One child in seven dies before their fifth birthday and one in 10 children is seriously underweight. Children are already in desperate need and their situation is only going to deteriorate over the coming months.
"Many Sudanese children already struggle to find enough to eat and many suffer from diseases that are easy to treat, like diarrhoea and pneumonia, which without treatment can be deadly. The returnees will only increase the numbers of children in desperate need and we really need your support now so we can make sure they stay healthy and have enough food."
The charity has already helped 6,200 people in Leer with blankets, tarpaulins, mosquito nets and sleeping mats but more money is needed to provide life-saving treatments for malnourishment and to combat killer diseases such as diarrhoea, malaria and pneumonia.
There are fears the secession vote starting on January 9 could spark a new civil war in Sudan.
To donate to Save the Children's southern Sudan appeal please go to www.savethechildren.org.uk/southernsudanappeal.