IOM, UNOCHA, UNHCR and UK government representatives have visited two open areas in Khartoum, where some 40,000 South Sudanese are living in makeshift shelters, waiting to return home.
The mission found thousands of residents living in precarious conditions with limited food, water, healthcare and sanitation, IOM said.Shanties made of plastic sheeting, wood and scavenged materials provide the Southerners with little protection from the elements, particularly during the rainy season.
The camps have no sanitation facilities, posing huge health risks especially when flooding occurs.
Many residents complained of harassment from host communities, authorities and land owners who frequently threaten to evict them.
Another estimated 3,500 South Sudanese returnees remain stranded at Kosti railway station for over one year, living in extreme hardship, with no access to basic services.
Thirty-two, including nine children, have died in the past eight months, mostly due to malaria and diarrhoea.
Representatives of those stranded at Kosti say that some 60 percent of the returnees are currently sick and lack funds to buy drugs.
The governments of Sudan and South Sudan estimate there are about 230,000 South Sudanese remaining in Sudan, many of whom have expressed a desire to return.