At least 40 people were burnt alive after a bus carrying flammable cargo crashed and burst into flames in Democratic of Congo's province of Kwilu, east of the capital Kinshasa, officials say.

The region's Governor Willy Itshunda told local media that out of 31 survivors, nine were seriously injured in Thursday's accident near Kiwawa village, some six hours from the capital where the bus was headed.

Despite it being unlawful to transport flammable material on passenger vehicles, the law is rarely enforced.

DR Congo's lack of roads and the poor state of public service vehicles also increase the chances of deadly accidents.

Of the 20,000 km (12,000 miles) of DR Congo's road network, only 10% is paved.