Fish are rotting in the basin of the world's second-largest river

The Brazilian government pledged $14m for relief efforts there.

The military has been distributing supplies and medicine to tens of thousands of people stranded by the dramatic drop in water levels.

But on Sunday an army general said the relief effort was being hampered by the lack of federal support.

Disease fear

A state of emergency was declared in all 61 municipalities of Brazil's Amazonas state as the drought started affecting towns and cities further downstream.

Witnesses say rivers and lakes have dried up completely, and millions of fish are rotting in the sun.

Low river levels are preventing boats - for many the only means of transport - from using the Amazon safely, leaving communities depending on airlifts for their survival.

The Brazilian government has already sent 50,000 food baskets to the area.

The national integration minister, Ciro Gomes, said that the priority was to stop the spread of diseases caused by contaminated drinking water.

'Linked' to hurricanes

The environmental campaign group Greenpeace has blamed deforestation and global warming for the drought.

It quoted scientists as saying that the burning of forests has raised temperatures in the Amazon, preventing the formation of clouds.

Brazilian government meteorologists, however, have said the drought is the result of unusually high temperatures in the Atlantic Ocean, that have also been linked to this year's devastating hurricanes.