A major highway in Mozambique has split after two bridges collapsed as a result of heavy flooding that has killed 25 people and displaces tens of thousands in the country, officials say.
Parts of the country are also without electricity after torrential rains knocked down 10 pylons, reports say.
Heavy rains have also devastated neighbouring Malawi, where 48 have been killed about 70,000 have been homeless.
The southern African states have been hit by late summer storms.
The bad weather is expected to continue for several days.
'Stranded in buses'
On Monday, Malawi's President Peter Mutharika declared a third of the country a disaster zone and urgently appealed for foreign aid.
In Mozambique, overland travel from the north to the centre and south has become impossible after two bridges collapsed on the EN1 highway, reports the BBC's Jose Tembe from the capital, Maputo.
There is growing concern for bus passengers stranded on either side of the bridges, he says.
They have been forced to sleep for two nights on the buses and are running out of food, our reporter adds.
The Licungo River is flowing so rapidly that it is impossible to reach them, even by boat, he says.
These are the worst floods on the Licungo since 1971, our correspondent says.
The Zambezi River has also risen beyond flood alert level on its middle and lower stretches, making some roads in the Zambezi basin impassable.
Mozambique's electricity utility EDM said it would take a week to restore power supply in the north.
Most of the north has been without electricity since Monday when 10 pylons were knocked down, according to Mozambique's independent television station STV.
The pylons are on the transmission lines carrying power from the Cahora Bassa dam to various parts of Mozambique.