About 60,000 Mozambicans have been evacuated from homes in the flooded Zambezi River valley in the last three days after weeks of heavy rain.
Mozambique was not prepared for the floods in 2000 and 2001
The army has used boats and helicopters to rescue people cut off by what officials are calling the worst flooding since 2001.
Rescue officials say another 100,000 people are still at risk.
Rising waters have cut road access to relocation centres already short of drinking water, food and shelter.
International aid agencies have launched an urgent appeal for funds and supplies for the flood victims.
'Worse than 2001'
Heavy rainfall across neighbouring Zimbabwe, Zambia and Malawi has poured into the reservoir of Mozambique's main hydro-electric dam, the Cahora Bassa, filling it to capacity.
Water has already been released, but officials say more flood gates must be opened to prevent the dam wall from bursting.
The situation is worst in the country's central region where the Zambezi River and its tributaries - the Shire and Revubue - have become swollen with surging waters.
Officials said 46,000 homes have been destroyed. Roads and bridges have been washed away, thousands of hectares of crops have been flooded and there are reports at least 29 people have been killed
The head of Mozambique's relief agency, Paulo Zucula, said they were expecting worse floods than those that devastated the country in 2001, killing 700 people. However, this time they were better prepared.
But many people arriving in the crowded relocation centres on higher ground have found them short of supplies and shelter.
And access roads have been cut by flooding.
One woman told Reuters news agency that the water struck her home at night last week and her family had lost everything.
"But now we are here without food and shelter and the government is saying there are no access roads to bring the food," said Julita Dinala.
Mozambique's Prime Minister Liusa Diogo has ordered the forcible evacuation of thousands of people in low-lying areas as more rains are expected to fall this week.
Some people have been reluctant to leave their homes, animals and crops.
The UN World Food Programme says that more than 250,000 people in Mozambique alone may need food assistance in the coming months because of the damage to crops and property.