Fire swept through a passenger bus in Zimbabwe, killing more than 40 people and injuring at least 20, some of whom suffered severe burns, authorities said on Friday.

A photograph posted on Twitter by the Zimbabwe Red Cross shows the remains of the bus that was completely incinerated late Thursday. The Red Cross said its teams responded to a “horrific accident” involving a bus heading to neighbouring South Africa at around midnight.

“Combustible material was allowed onto the bus, thus causing a conflagration which entrapped, scalded and consumed innocent passengers,” President Emmerson Mnangagwa said in a condolence message.

Mnangagwa said the government should “take appropriate measures which comprehensively deal with this growing menace on our roads".

The accident happened in Gwanda district, about 550 kilometres south of Harare, Zimbabwe's capital.

Police spokeswoman Charity Charamba confirmed a death toll of more than 40.

Last week, a collision between two buses in Zimbabwe killed 50 people and injured about 80.