Scores of children caught up in the conflict in eastern Democratic Republic of the Congo (DRC) have been subjected to sexual violence including rape by armed men, according to the United Nations Children's Fund.

The targeting of children has soared to unprecedented levels in recent weeks, UNICEF Executive Director Catherine Russell warned on Thursday, making an urgent appeal for the violence to stop as Rwanda-backed M23 rebels expand their footprint, clashing with Congolese forces and their allied militias. "In North and South Kivu provinces, we are receiving horrific reports of grave violations against children by parties to the conflict, including rape and other forms of sexual violence at levels surpassing anything we have seen in recent years," Russell said in a statement.

Sharing the stories of some survivors, she said: "One mother recounted to our staff how her six daughters, the youngest just 12 years old, were systematically raped by armed men while searching for food." UNICEF's accusation came as the conflict in the mineral-rich region shows no signs of abating, as M23, which captured North Kivu's capital Goma last month, pushes further south.

Thousands have been killed and tens of thousands more displaced, the UN has said.