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.
In the past four months, more than 450,000 people in ethnically-mixed eastern Congo have fled their homes.
The UN Humanitarian Affairs chief Valerie Amos, on a visit to the Kigeme refugee camp in neighbouring southern Rwanda, said all partners in the region had to help solve the crisis.
Amos said: “The situation here is [so] terrible, people have come here spontaneously. We are doing our best to respond, but thousands of people [have been] displaced in a very short period of time. Everything has to be done, politically, for fighting to stop.”
The North and South Kivu provinces have seen hundreds of thousands uprooted, some fleeing to Uganda and Rwanda.
A recent surge in fighting drew government troops to reinforce the provincial capital Goma, exposing other areas.
Renegade soldiers known as the 23 March Movement (M23) have clashed with national army troops.
They launched their rebellion earlier this year after accusing the government of failing to uphold its end of a March 2009 peace deal to reintegrate them.
African leaders of the Great Lakes region, after a two-day summit in Uganda last week, said they would impose sanctions on any party obstructing peace in the DRC.
Rwanda denied allegations by UN experts that Rwandan military officials have supplied M23 with equipment and recruits.
Uganda rejected similar allegations.
The leaders meeting in Kampala called for a “complete halt” to the fighting.
Aid agencies are warning that a cholera epidemic on the borders of Sierra Leone and Guinea is worsening.
French charity Médecins sans Frontières says more than 250 people have died across West Africa
Doctors say hygiene and sanitation in many slums and urban areas as well as the onset of the rainy season are to blame.
More than 13,000 people have been hospitalised since February.
“They are crying of cramps in their feet and even their hands are cramping. They are falling down, they have got dizziness. Some of them say: ‘I want to die, I’m tired, I’m tired of this disease.’ At the end of the day some of them die,” said Fatmata Kargbo, a nurse for Médecins sans Frontières.
Cholera spreads quickly through contaminated water or food causing severe diarrhoea and vomiting.
Since the last major epidemic in 2007, many people in the region have lost their immunity to the disease.
Medical teams are opening additional treatment centres in Sierra Leone’s capital Freetown and Conakry in Guinea.
Doctors estimate that with proper treatment fewer than one percent of cholera patients should die. Vaccines are not the only solution to prevent outbreaks, experts say that poor living conditions must also be tackled.