The fuel truck collided with another vehicle and toppled over late Saturday near Malanga, some 315 kilometers (195 miles) northwest of Nairobi, on the busy highway between Kisumu and the border with Uganda.
Onlookers rushed to the scene with jerrycans but the cargo exploded, engulfing those around in a terrible fireball.
“It burst into flames as they scooped fuel that was flowing,” said Charles Chacha, a local police chief in Siaya County where the accident occurred.
“We counted twelve bodies at the scene. Another person died in hospital from their injuries.”
Fire crews arrived on the scene two hours later to douse the inferno while those injured in the blast were taken to hospital.
“Many others have been taken to hospital with serious burns and they include young children,” Chacha said.
The cause of the explosion is not yet known.
Images broadcast by Kenyan media showed the blazing tanker lighting up the night sky and in the morning following, crowds gaping at the twisted, smoldering wreckage.
Deadly fuel truck accidents along perilous roads are not uncommon in Kenya and the wider East Africa region.
In 2009, more than 100 people were killed when a petrol tanker overturned northwest of Nairobi and an explosion consumed those gathering to collect leaking fuel.
More recently, at least 100 people were killed when a tanker exploded in Tanzania in 2019 while in 2015 more than 200 perished in a similar accident in South Sudan.