Swathes of countryside previously safe for humanitarian operations are now under the control of renegade general, Laurent Nkunda, head of the rebel Congrès National pour la Défense du Peuple (CNDP).
Despite his promises to open relief corridors for aid convoys, few agencies have judged it safe enough to truck widespread help into the worst-affected areas.
This has left tens of thousands of people trapped where they fled with little food, shelter or medical help. It is still too early to calculate how many need assistance.
"We are still too afraid to go to the fields to find food but now the small amounts which were on sale in the market are running out and are very expensive," Louis Kakule, a 52-year-old farmer, told IRIN by telephone from Kiwanja.
The town lies in the heart of the territory captured by the CNDP from retreating government soldiers, 85km north of Goma, the capital of North Kivu province and headquarters of the international aid operation for eastern Congo.
"Since the rebels came, we have seen no help from outsiders and now the situation is becoming very bad," he said.
Kakule, his wife and nine children, fled to a UN military outpost as rebels battled Mai Mai militia last week. However, they have not received any outside assistance.
"We are working as hard as we can to get immediate help to all of the people who need it," said Marcus Prior, spokesman in Goma for the UN World Food Programme (WFP).
"But we have to be very careful about how we move food about, for any number of reasons, not least of which is the number of armed groups who might choose to target a slow-moving convoy of food. We also do not yet have a clear picture of who has gone where after the latest surge in fighting."
Simply "dumping food off the back of a truck" was not an option, Prior added, because it could cause even greater problems as desperate people stampede for rations and the most vulnerable - women, children and the sick - end up with the least.
There have been well-organised and substantial hand-outs in established camps around Goma and at Kibati, a village 11km north of the city, which was swamped with 65,000 people who fled the advance of Nkunda's forces southwards.
On 10 November, WFP completed the distribution of 10 days' worth of food rations to 135,000 people in six camps close to Goma. The International Committee of the Red Cross (ICRC) spent four days handing out beans, maize, oil and salt to a further 65,000 around Kibati.
However, the challenge for aid workers attempting to respond to the crisis was laid bare as sustained gun and mortar clashes broke out on 7 November at the frontline less than 2km north of where thousands of displaced had settled and food was being distributed.
As Congo's army, the FARDC, fought Nkunda's CNDP, almost half of Kibati's newly arrived population fled again, south into Goma.
"There is nowhere we can feel safe," said Danzira Maniriho, 20, as she lifted her six-month-old son Samuel on to her back and set off south as the fighting flared.
"I have run from Rugare to Kibumba, then from Kibumba to Kibati, then to Goma and back here again, and now I am going back to Goma. All the time, until today, we have had no food, only bananas that we have stolen from the fields," she told IRIN.
Armed escort controversy
The need for food deliveries and distributions to be protected from fighting has prompted calls for aid convoys to drive under armed escort, provided by the UN Mission in Congo, MONUC.
But such proposals were questioned by Médecins Sans Frontières. "Armed aid convoys may aim to improve access for humanitarian aid groups, but they actually risk reducing access to the populations," said Anne Taylor, MSF head of mission in Goma.
"There is a risk of aid being manipulated by political or military actors and of humanitarian actors being seen as parties to the conflict."
WFP registration of those who most need assistance was due to be carried out on 12 November around Rutshuru district and food deliveries were expected by the end of the week, Prior said.
Emergency aid in seven aircraft sent by Britain and the US arrived in Goma by Wednesday, carrying plastic sheeting, buckets and blankets.
"These supplies will help contain the spread of cholera and diarrhoea, both extremely contagious diseases on the rise in nearly all internally displaced person settlements in North Kivu," said Pierrette Vu Thi, Congo representative for the UN Children's Fund, UNICEF.