The United Nations has condemned the abduction of some 89 schoolboys by an armed group in South Sudan.

UNICEF says the boys, some as young 13, were taken near Malakal in the north of the country. A UNICEF education team reported that the children were abducted while doing their exams.

It warns that the actual number could be much higher.

The incident happened in the community of Wau Shilluk in Upper Nile State, where thousands of people have been internally displaced by the ongoing conflict.

According to witnesses, armed soldiers surrounded the community and searched house by house.

Boys older than 12 years of age were taken away by force.

UNICEF representative in South Sudan, Jonathan Veitch, urged the group to immediately release the children.

"The recruitment and use of children by armed forces destroys families and communities. Children are exposed to incomprehensible levels of violence, they lose their families and their chance to go to school," he said.

It comes just a fortnight after Nobel Peace Prize winner Malala Yousafzai launched a scathing attack on the international community, for not doing more to help free more than 200 Nigerian schoolgirls from Boko Haram.

The Islamist group took the 276 girls from a boarding school in the village of Chibok, in Borno state, north Nigeria, on April 14th last year.

Ms Yousafzai said: "If these girls were the children of politically or financially powerful parents, much more would be done to free them. But they come from an impoverished area of northeast Nigeria and sadly little has changed since they were kidnapped."