Mozambique's top disaster official says his country has the use of only one UN helicopter to get supplies to thousands of people displaced by severe flooding.
The floods have forced tens of thousands from their homes
Paulo Zucula told Reuters news agency that a number of evacuation centres were no longer accessible by road.
He warned that many of those who had reached the camps could die if they did not get enough food and clean water.
Severe flooding in the Zambezi Valley has forced more than 120,000 people from their homes in recent weeks.
Mr Zucula, who is in Caia, where the central relief office has been set up, told Reuters that at least 4,000 people in the area had not received food or drinking water.
"They are starving and some diseases such as malaria and cholera are looming," he said.
Mr Zucula said the single UN helicopter Mozambique had was the only way to get supplies to those displaced.
"We were not prepared... it's another disaster," he said.
In 2000 and 2001, 700 people were reported to have died and 500,000 were displaced in severe flooding.
About 40 people have died in the latest floods, which began in December.
However aid workers say the casualties could rise in the coming weeks, as there is little hope of an immediate let-up.