Aid agencies in the Democratic Republic of Congo say they are struggling to deliver aid to hundreds of thousands of civilians displaced by fighting.
Roads through villages have become ghost towns
The UN says it is hard to reach 300,000 people in the east who rely on food aid, while 150,000 remain out of reach.
Battles have resumed between the army and fighters loyal to a renegade general forcing more people to flee.
The army says some 100 fighters, including 85 rebels, have been killed near Karuba, some 40km from Goma.
Colonel Delphin Kahimbi said they had been in control of the town, north-west of Goma, since Tuesday.
"The enemy has abandoned 85 bodies on the ground," he told AFP news agency. Sixteen of his own forces also died.
Both the army and Gen Laurent Nkunda accuse the other of breaking a recent ceasefire.
A BBC reporter says women have been arriving at a hospital with severely malnourished children in their arms.
Gen Nkunda says he is fighting to protect DR Congo's Tutsis minority.
The government has given the rebel general an ultimatum of 15 October to cease hostilities and integrate his forces into the army or face tough action.
But the former commander of UN forces in eastern DR Congo told the BBC that fighting Gen Nkunda and his men is not the solution to the problem.
"If you like it or not Nkunda is a factor in North Kivu and the factor of dealing and addressing the needs and legitimate demands of a minority is something you cannot ignore," Maj Gen Patrick Cammaerte told the BBC's Network Africa programme.
"Unless the government of the DRC is willing to address the minority problem politically, and taking away doing that, the arguments of Mr Nkunda, there will be no solution."
The UN has 17,600 peacekeepers in DR Congo - the largest such force in the world, 4,300 of them in North Kivu alone.
The BBC's Arnaud Zajtman in Masisi says the sound of heavy artillery and shelling echoed through the area's green hills on Tuesday.
KEY FORCES IN THE KIVUS
FLNK - new group made up mainly of Congolese Mai Mai with some Rwandan Hutus formerly in the FDLR
FDLR - Hutu militia made up of former Rwandan soldiers and others who fled into Congo after the 1994 genocide
Gen Laurent Nkunda, with an estimated 5,000 soldiers
Monuc - UN Mission in the DR Congo
Government forces and the rebels have been fighting near Karuba for the second day.
As a result, armed men with bullet wounds kept arriving at the hospital of Masisi, a small government-held town near a stronghold of Gen Nkunda.
He said some of those injured were members of the regular army, others belonged to the newly created militia groups.
Some of them were Rwandan Hutu militiamen who it is alleged took part in the genocide in neighbouring Rwanda in 1994.
They were also caught up in the fighting and have been admitted to hospital in recent weeks.
Gen Nkunda and his men said they took up arms to fight the Rwandan Hutu militiamen, whom they perceived as a threat.
But DR Congo's army says they are trying to disarm them.
Medical staff have had to open feeding centres in Masisi, but an aid worker with French aid group Medecins Sans Frontieres said bringing medical supplies to the hospital was a nightmare because the different armed groups have established roadblocks.
Children in the area are said to be at risk of abduction
The road stretches through villages that have become ghost towns.
Families walk on the side of the road, their few belongings on their head, our reporter says.
More than 300,000 civilians have already fled to displaced camps where they rely on humanitarian assistance.
But our correspondent says in Masisi there is a camp of another sort. About 400 young men and 70 children have gathered together in an open field.
They say they have escaped from forced recruitment operated by the rebels of Gen Nkunda in the schools of the region.
They refuse to join any of the many armed groups in the area, our reporter says.
Our correspondent says they want peace to return so they can go back to school.
But in the present climate for many children it is impossible to go to school.