More than 900 000 people have been displaced by violence in the strife-ridden eastern DRC region of North Kivu.
This figure is up about 500 000 on the figure made public in April, according to the UN on Thursday.
The steep rise was due to intense fighting between the army and rebel group M23 around the regional capital Goma, said Gert Weskereen of UN refugee agency UNHCR.
Goma was taken by rebels without much resistance on November 23, but they left the mining hub eight days later under pressure from neighbouring countries and set up positions nearby.
Weskereen said 914 000 displaced people had been registered in North Kivu so far, but would not rule out that some of them had been counted several times.
Since the end of the fighting about two weeks ago, people have been returning to the Rutshuru region north of Goma, which had been taken by the rebels in July.
So far, 9 000 households, or about 27 000 people, have returned.
The WFP said refugees had settled down in 19 areas around Goma. Only one camp is being managed by Congolese authorities.
Others are improvised sites set up around facilities such as schools and churches.
Nona Zicherman of Unicef put the proportion of displaced people who have been accommodated by host families at 80 percent.
Of these, 160 000 received food aid, said the WFP's Fabienne Pompey. According to a Unicef tally, 751 children were reported missing by their families, separated from them in the fighting and chaos created by the rebel advance through the chronically volatile but mineral-rich east.
Only 84 have so far been able to return to their families.
The M23's lightning capture of Goma eight months after the rebels launched an uprising against the government had raised fears of a wider war and a major humanitarian crisis in the DRC.
Draft of demands
Kinshasa and the M23, which was formed by army mutineers, opened talks on Sunday in the Ugandan capital, where the rebels are expected to present a draft of demands to the government, including a call for major political reform for the war-weary region.
The M23 was founded by former fighters in a Tutsi rebel group whose members were integrated into the regular army under a 2009 peace deal that they claim was never fully implemented.
Several of its leaders have been hit by UN sanctions over alleged atrocities. – Sapa-AFP