"The fighting has meant that we and our partners have not been able to access most of these areas," he said. "Only Mugunga III just outside Goma can be currently visited."
North and South Kivu face the greatest risk.
The Kivus are considered mineral-rich in a country known for its vast reserves of diamonds, gold and copper.
The area's potential for wealth has been plundered by greedy warlords. Civil wars -- most recently in the 1990s through 2003 -- have left millions dead and displaced entire generations.
On Tuesday, the United Nations moved all but a core team to Rwanda to avoid casualties and urged armed parties to ensure civilians' safety.
"In Goma, there have been reports of 60 assaults on civilians to our partners," Edwards said Friday. "Our partners are telling us eight people have been killed, and houses and shops have been looted."
Killings included six women, including one who was pregnant and an additional infant, according to Rupert Colville, a spokesman for the U.N. High Commissioner for Human Rights.
The fighting between M23 and the Congolese army has left the Kivus vulnerable to other armed groups, raising the possibility of the Lord's Resistance Army abducting children, said Marixie Mercado, a spokeswoman for the U.N. children's agency.
"There are other groups operating in the area, which raises the likelihood of recruitment of children," she said.
And the risks are not limited to violence.
"Before the crisis started, there were already 27,000 cases of cholera reported in the country," she said. " Running water in Goma has just been restored. It had been shut off for over a week and there are huge numbers of children collecting water from Lake Kivu which obviously raises the risk of disease spreading."
The U.N.'s refugee agency estimates that more than 589,000 people have been displaced in North and South Kivu since the beginning of the year. Oxfam estimates that 230,000 are affected by this crisis alone.