Nine people have been killed and at least 20 others seriously injured in a fiery road crash on Nairobi-Mombasa highway near Sultan Hamud in Makueni County.

They died after a bus, belonging to Mombasa-based BusCar company, and a lorry burst into flames following a head-on collision early Wednesday morning.

Makueni County Commissioner Mohammed Maalim confirmed the deaths, saying the injured had been rushed to Kilome Nursing Home for medication.

"The vehicles collided head-on and went up in flames," said Mr Maalim, describing the crash as "a very bad one".

The bus was heading towards Mombasa when the disaster struck.

Mr Maalim said police were investigating the actual cause and circumstances under which the smash-up happened.

The dead were taken to Makindu Hospital mortuary.