As many as a half a million people have been forced from their homes in the Democratic Republic of Congo, according to Oxfam.
The charity says a three month long internal conflict is causing a major humanitarian crisis in the east of the country.
The Congolese government is fighting a rebel movement called M23, said to be backed by neighbouring Rwanda and Uganda.
A spokesperson for Oxfam has described the situation there as “chaotic”.
Another charity Medicins Sans Frontiers is worried about an outbreak of cholera in impromptu refugee camps in North Kivu province.
“This centre is short on water, no latrines, no waste disposal. There is overcrowding and hygiene rules are not being respected,” said Dr Christian Masudi.
The aid agency has set up an isolation clinic to treat those affected by the disease.
The United Nations’ aid chief Valerie Amos visited the area on Tuesday to see how NGOs are coping with the crisis.
Aid agencies have appealed for more than 630 million euros for humanitarian support but claim there has been a global funding shortfall.
A regional summit is being held in Uganda’s capital Kampala in an attempt to end to the conflict. The DRC’s neighbours have denied any involvement in the rebellion.