By Greg Barrow in Maputo

From above it looks as if a huge tidal wave of brown water has swept through the Save river valley.

Trees have been uprooted, houses lie in ruins and debris is floating in the floodwater. Those who survive the flooding have been stranded on rooftops and in trees.

Beneath them the bloated corpses of livestock float in the waters.

Two South African helicopters chartered by the Mozambican Government are doing what they can to rescue the survivors. Pilots say some people have been trapped in trees for days without food or water.

As the helicopters fly above them the people wave frantically, motioning to their mouths and stomachs with their hands to show that they are hungry.

When the rescue helicopters come to winch them to safety there's a desperate scramble for whatever belongings the people can grab.

Over stretched rescue effort

The helicopters have lifted around 300 survivors to higher ground but their work is difficult, fuel supplies are low in the area and pilots say there's a lack of co-ordination in caring for the flood victims.

The South African national defence force says it has more helicopters and planes on standby to fly up to the Save area, where up to 40,000 people are believed to be trapped by the floods.

They would have gone earlier but further heavy flooding in Gaza province has prevented them from moving to other areas in need.