Aid has started to reach some of the 100,000 people affected by famine in parts of South Sudan.

Three years of civil war have driven families into the marshes of the Nile to hide from the fighting, and the UN and other agencies have been struggling to get access to deliver food.

BBC Africa Correspondent Alastair Leithead travelled to the rebel-held town Thonyor in Leer County - where people have been told to gather to get help.