Beira, Mozambique– They waited for rescue for days, clinging on to trees and rooftops, after a powerful cyclone tore through Mozambique and triggered flash floods in what the UN has called “one of the worst weather-related catastrophes in the history of Africa”.

Many said they survived by drinking boiled water.

When rescue workers arrived in boats and helicopters, most had nothing more than the clothes on their backs, and their feet were swollen from days of waiting in water.

Hundreds were taken to the Escola Secundaria Samora Machel in the city of Beira.

Aid agencies are providing survivors with a bucket of drinking water and a large pot of rice, but other basics are still lacking. Some are relieved just to be alive, but said they fear for those left-behind.

“I’m happy that at least some family members have been rescued,” said Otilla Sacur. “But most of them are still [in the flooded areas]. That makes me very sad.”

Cyclone Idai, which also hit Zimbabwe and Malawi, killed more than 700 people and washed away entire villages in the affected-region.

In Mozambique, thousands are still waiting to be rescued, aid workers said, while the United Nations some 1.85 million people need urgent help.

“At least one million children need urgent assistance and this number may well grow. We fear that whole villages have been washed away in places we have yet to reach,” Antonio Guterres, the UN chief, told reporters on Tuesday.