The city of Goma has been swollen by thousands of refugees desperate for food
Fears are growing for the fate of more than 250,000 civilians forced to flee their homes by fierce fighting in eastern Democratic Republic of Congo.
A ceasefire between government troops and rebels is holding but the situation is desperate, with chaotic scenes reported at aid distribution centres.
Families stormed one camp in Kibati as others tried to scale the walls.
Meanwhile, European ministers have met Congolese President Joseph Kabila as part of efforts to end the crisis.
French Foreign Minister Bernard Kouchner and his British counterpart, David Miliband, said they had urged the full implementation of existing peace agreements between Congo and neighbouring Rwanda, and the disarming of militias.
"Around the world, people are seeing the makings of a humanitarian crisis and it's vital that politics is used to reverse a further round of deaths and killings," Mr Miliband said.
The pair have flown to Goma, the provincial capital of the volatile east, to see for themselves the scale of the humanitarian crisis.
They will then take a helicopter to Rwanda for talks with President Paul Kagame, whose country has been accused of aiding the Tutsi rebel assault in the Democratic Republic of Congo.
Earlier, the British foreign minister for Africa, Mark Malloch Brown, said the first priority to stabilise the situation should be the immediate strengthening of the UN contingent based in Goma, where he said there were only about 850 combat troops.
Lord Malloch Brown said the EU was also drawing up a contingency plan for sending soldiers to Congo, if the UN force proved insufficient. France proposed this week that the EU send up to 1,500 troops.
The BBC's Peter Greste says the scene was dangerously chaotic at the UN Children's Fund (Unicef) feeding centre in the Kibati camp for displaced people, 20km (12 miles) north of Goma.
The agency brought in high energy biscuits, emergency food for children, and in minutes, hundreds - perhaps thousands - of people rushed the gates, he says.
Our correspondent says there was a huge crush of desperate families pressing against the fence while others were trying to scale the walls.
He says this is not the way Unicef normally does things, but because the need is so urgent and people are so hungry, they decided to dispense with the usual registration process.
Food is at last beginning to trickle in but it is nowhere near enough for all the children, many of whom are showing symptoms of serious diseases, he adds.
Some refugees are trying to return to their homes, journeying on foot through territory now controlled by the forces of renegade Gen Laurent Nkunda.
The general - who says he is protecting his Tutsi people against the Hutus linked to the 1994 genocide in Rwanda - has halted his troops close to Goma.
The UN refugee agency, the UNHCR, said camps sheltering 50,000 refugees in Rutshuru, 90km (56 miles) north of Goma, had been forcibly emptied, looted and then razed.
The UN has more than 17,000 peacekeeping troops in DR Congo - the largest UN force in the world - but correspondents say it is struggling to cope with the scale of the crisis.
On Friday, the Rwandan and Congolese presidents agreed to attend a regional summit in the Kenyan capital, Nairobi, in the coming weeks to try to end the fighting.
EU Development and Humanitarian Aid Commissioner Louis Michel said both leaders had been sincere about "opting for dialogue and putting an end to the reasons that are undermining the east" of DR Congo following two days of talks in Kinshasa and the Rwandan capital, Kigali.
"They are both fully agreed on the idea of having this summit," he told the BBC.
But Gen Nkunda had not yet been asked to join the talks, he added.
The origin of the ongoing conflict in eastern DR Congo is the 1994 genocide in Rwanda.
Gen Nkunda says he is fighting to protect his Tutsi community from attack by Rwandan Hutu rebels, some of whom are accused of taking part in the genocide.
The Congolese government has often promised to stop Hutu forces from using its territory, but has not done so.
There have also been accusations of collusion between DR Congo's army and Hutu guerrillas.
The Congolese government, for its part, has accused Rwanda of backing Gen Nkunda.
Rwanda denies this, but it has twice invaded its much larger neighbour in recent years.