These efforts come days after a powerful cyclone triggered flash floods, submerging entire villages and wiping out communities across southeastern Africa.
Aid workers on Wednesday spoke of women trapped in trees "throwing their babies" onto rescue boats. They talked of plucking people from head-deep water, only to strand them in patches of land where the water reached their ankles.
Cyclone Idai hit Beira with winds of up to 170 kilometres per hour last Thursday, then moved inland to Zimbabwe and Malawi, killing hundreds and putting the lives of millions at risk.
United Nations officials say this could be the worst ever weather-related disaster to have struck the southern hemisphere.
Authorities say at least 217 people have died in Mozambique, 98 in Zimbabwe and 56 in Malawi, but the death toll is likely to rise as rescuers continue to find bodies.
Mozambican President Filipe Nyusi, who has declared a national emergency and three days of mourning starting on Wednesday, has warned that the eventual number of those killed in the cyclone and flooding could rise to more than 1,000