There are signs that the acute food crisis affecting nearly one-million people in southern Sudan is worsening, despite a massive international aid effort.

The BBC East Africa correspondent, who's visited the worst-hit region of Bar al-Gazal, says aid agencies now estimate that the number of people needing food is three times greater than first thought.

The United Nations' Operation Lifeline says it's constantly discovering new pockets of need and finding people in a worse state than expected.

The medical charity, Medecins Sans Frontieres, says that in some cases half the severely malnourished children in its feeding centres are deteriorating because not enough food is getting through.

Our correspondent says two years of drought and the long-running civil war in southern Sudan have created a disaster that could still become a catastrophe.