With Congo's army diverted to eastern Congo, new militia groups have arisen as older ones reassert themselves, killing hundreds of civilians.
"Vast swathes of the east have descended into chaos with no government or security presence," the British charity Oxfam's country director Elodie Martel said.
Underscoring the severity of the situation, UN humanitarian chief Baroness Valerie Amos arrived in Goma on Tuesday and is to visit some of the 280 000 people who have fled their homes since mutinying soldiers launched the M23 rebellion in April. But security is so poor that Amos was forced to cancel planned trips to the mining town of Walikale and the seat of the rebellion at Rutshuru town, 75km north of Goma.
The rebels now control huge swathes of mineral-rich eastern Congo.
As the 150 000-strong Congolese army, backed by 20 000 UN peacekeepers, has redeployed against M23 rebels in North Kivu province, fighting has spread to villages and towns, with the combatants often aiming to gain control of mines.
Oxfam researcher Marie Cacace said the group's report stems from information from village protection committees which report to local authorities.
"Hundreds of people have been killed in attacks against villages in South Kivu, houses burnt and people kidnapped according to local and UN reports," said the Oxfam statement, adding that recruitment of child soldiers is widespread, as is forced labour.
Oxfam called for regional leaders meeting to discuss the crisis on Tuesday and Wednesday in neighbouring Uganda to put the protection of civilians and a resolution to the regional dimensions of the conflict at the top of their agenda.
Supporting the rebellion
Rwanda and Uganda have been implicated in supporting the rebellion, though both countries deny it. Their leaders are expected at Tuesday's summit.
Rebels control hills within 30km of the eastern provincial capital Goma. Just miles away at Kanyaruchinya, people fleeing the fighting have taken refuge in a Catholic church and school. Those who cannot find space in buildings, or the homes of friends and relatives, have built makeshift huts of twigs and leaves.
Raspy coughs and sniffles among children at the impromptu camp are a sign of the increasing number of respiratory illnesses being treated by Médecins Sans Frontières. The first case of cholera was discovered at the camp last week. By Monday, the doctors said they were treating 58 cases of cholera and that one child had died at a tented isolation unit. Nurse Chantal Kaghoma said three people had died of cholera in the camp.
Cholera is endemic in the region. Since January more than 20 000 cases of cholera and 481 deaths have been reported across the country.
"The humanitarian consequences of the conflict are huge," Martel said.
Congo suffered back-to-back civil wars that drew in the armies of a half dozen nations in a scramble for its vast mineral resources that killed as many as five million people. An internationally negotiated peace deal was signed in 2002 but the conflict never ended in east Congo. – Sapa-AP