"WFP has been rescuing approximately 900 people each day," the Rome-based UN agency said.
It was conducting search and rescue missions using 14 helicopters and six fixed-wing aircraft. Seven of the helicopters were from the South African defence force and seven from the United Kingdom.
"Estimates indicate that between 800,000 and 1 million people have been made homeless in the region," it added.
The WFP says it has shuttled more than 1,200 tonnes of food to 50 key delivery points in Mozambique.
Meanwhile, the UN Food and Agriculture Organization (FAO) launched an urgent international appeal to help more than 300,000 farmers in Mozambique.
"The world is witnessing a tragedy of enormous scope in Mozambique," said Jacques Diouf, FAO's Director-General. "A disaster of this scope would tax the resources of even the most advanced countries. But in the case of a developing country like Mozambique, the means to cope are just not there."
Meanwhile, the UN's Office for the Coordination of Humanitiarian Affairs (OCHA) is stressing the importance of small boat operations to reach flood victims. OCHA also flagged the need for assistance to victims of flooding in Zimbabwe, Botswana and Swaziland, and has fielded a disaster assessment team to work with authorities and UN agencies already on the ground.