Water-borne diseases are said to be prevalent in areas inundated by flash flooding.
“For the other 250,000 or thereabouts there is nothing in the kitchen. Their crops have been destroyed,” he said.
Ethiopia, Rwanda and Sudan are also affected, with hundreds of thousands now at risk of water-borne disease.
Meanwhile, 18 people are said to have been killed after flooding had hit dozens of villages in northern Ghana.
Alhassan Samari, the minister in charge of the relief effort, said last week that at least six people had died in the flooding caused by torrential rains.
However, local residents had warned the death toll may rise further.
As many as 260, 873 people have reportedly lost their homes due to the flooding.
Residents across west Africa are said to have been displaced as torrential rains to continue to persist.