Geneva - Children have been recruited as soldiers by rebel groups in the Democratic Republic of Congo and woman and girls have suffered sexual violence, UN officials said Friday.

"The rebels need to immediately release the children," said Veronique Taveau of UNICEF, the UN Children's Fund, adding that her organization was using the radio in Congo to issue this message to the fighters.

She said at least 37 cases of child soldiers have been identified so far, with the possibility that many more are being forced into service for the militant groups, though it would take time to get a more accurate number.

Teenage children were given roles of regular soldiers while the younger ones were acting as manual labourers.

Also, sexual violence against women and young girls is being used as a "weapon of war," Elizabeth Roesch of CARE International, an aid group, told Deutche Presse-Agentur dpa from Goma.

Some 3,500 cases of rape were reported since January but the number is likely higher as many women do not report the violence.

The women were also being forced into domestic labour, aid workers said.

The violence against women was "a tactic to humiliate and terrorize," said Roesch.

Meanwhile, many children arriving with groups of refugees to areas like Goma were unaccompanied, as their parents either were killed or returned to their villages but left their children behind in relative safety.

Aid workers expressed concern over the "cyclical nature" of the violence, saying that rape and recruiting child soldiers were tactics used in the previous conflicts in the region.

The World Health Organization said there were 300 reported cases of cholera and also outbreaks of measles.

While food and medicine distributions were ongoing, some areas remained inaccessible due to the danger posed to the aid workers and shoddy infrastructure.

Approximately 253,000 people have fled their homes in North Kivu since September, on top of some 800,000 already internally displaced individuals from previous hostilities.

UN officials said civilians in camps still faced dangers from the fighting, as they could get caught in the crossfire. (dpa)