There has been a marked rise in the forced recruitment and abduction of children by armed groups in the Democratic Republic of Congo, a UN official says.

Virginia Gamba, the special representative of the UN Secretary-General for children in armed conflict, said they were often used as forced labour, or sex slaves.

She added that a belief in magic meant some children were used as a talisman in an attempt to make fighters invincible.

According to the latest UN report, in the past three years children were the victims of more than 11,000 grave violations across DR Congo.