One of the buses tried to pass two large trucks on a stretch of the road where overtaking is prohibited, an official said.
The bus left the road, rolled down a slope and crashed, ripping off the roof. A police official said the bus was not licensed to operate at night.
The fire broke out just as local residents had reached the scene to gather leaking fuel.
Hundreds of people were injured after a gasoline tanker exploded while it was unloading at a gas station, an emergency official said.
Badly injured in a car wreck in South Africa, the woman was pronounced dead by an ambulance crew. But she was later found to be alive and moved to a hospital, where she remains in critical condition.