UN peacekeepers have "failed" the victims of mass rape in eastern DR Congo, a senior UN official has said.

Atul Khare told the Security Council that the scale of systematic rape by armed rebels was far worse than feared.

He said that up to 500 women and children were now believed raped in recent weeks - more than double the previously reported figure.

He called for the prosecution of Rwandan and Congolese rebels who are blamed for many of the attacks.

"At the same time a concerted response from the government, from the international community is needed to maintain pressure on the perpetrators of these rapes and to bring them to justice," he told the BBC's World Today programme.