Cyclone winds and floods that swept across southeastern Africa have affected more than 2.6 million people and could rank as one of the worst weather-related disasters recorded in the southern hemisphere.

Rescue crews were still struggling to reach victims on Wednesday, six days after Cyclone Idai raced in at speeds of up to 170 kph from the Indian Ocean into Mozambique, then its inland neighbours Zimbabwe and Malawi.

Aid groups said many survivors were trapped, clinging to trees and crammed on rooftops in remote areas, surrounded by wrecked roads, flattened buildings and submerged villages.

"This is the worst humanitarian crisis in Mozambique's recent history," said Jamie LeSueur, who is leading rescue efforts in the hard-hit city of Beira for the International Federation of Red Cross and Red Crescent Societies.

The organisation said large areas to the west of Beira were severely flooded, and in places close to the Buzi and Pungwe rivers, flood waters are metres deep, completely submerging homes, telephone poles and trees.

"The scale of suffering and loss is still not clear, and we expect that the number of people affected as well as the number of people who have lost their lives may rise," said LeSueur.

Death toll in the flood disaster has crossed 200 in Mozambique, according to President Filipe Nyusi.

Nyusi said on Monday he had flown over some of the worst-hit zones, seen bodies floating in rivers and now estimated more than 1,000 people may have died.

The cyclone hit land near Beira on Thursday and moved inland throughout the weekend, leaving heavy rains in its trail on Tuesday. (Aljazeera)

• People are escorted to safety by aid workers at the airport of the coastal city of Beira in central Mozambique

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