(AFP) - Mozambique has cancelled flights to several domestic destinations as a tropical cyclone, potentially the strongest to hit the country in nearly two decades, approached threatening to bring chaos to southern Africa.

The wave of cancellations came as the UN warned that "tropical cyclone Idai has regained intensity and is expected to make landfall near Beira city in central Mozambique" later Thursday.

At least 126 people have been killed in Mozambique, Malawi and South Africa as heavy rains hit southeastern Africa over the past week, affecting more than one million people, officials said.

The United Nations Office for the Coordination of Humanitarian Affairs warned that the incoming storm could bring winds of up to 190 kilometres per hour (118 miles per hour).

That would make it the strongest tropical cyclone to make landfall in Mozambique since Tropical Cyclone Eline which struck the country in February 2000, claiming at least 800 lives.

Another storm in 2015 left more than 100 people dead.

Mozambique is prone to extreme weather events and as the storm approached, the coastal city of Beira was hit by winds of more than 170 kph, the National Meteorological Institute said, with Radio Mocambique reporting several homes had been destroyed and roads cut off.

Late on Wednesday, Mozambique's national carrier LAM said it was cancelling all flights to Beira and Quelimane, which is also on the coast, as well as to Chomoio, which is inland.

But many passengers were unaware of the cancellations, leaving hundreds stranded at Maputo International Airport.

The UN warned that cyclone Idai would bring strong winds, heavy rains and storm surges which would likely last through the weekend.

"Substantial devastation with massive flooding both from river and sea is expected" when Idai makes landfall, South African charity Gift of the Givers said, indicating it was ready to deploy 70 rescue staff, along with 4x4 vehicles, boats, and jetskis to help with rescue efforts.

© Agence France-Presse