The truck exploded at around 11:30pm local time in Embakasi district, Nairobi and ignited “a huge ball of fire,” according to a government spokesperson.
Housing, businesses and vehicles were damaged in the explosion and fire is believed to have engulfed apartment buildings.
Embakasi police chief Wesley Kimeto said a child was among those who died in the explosion, adding that the death toll could rise.
The Kenya Red Cross said it had taken 271 people to hospital and treated 27 others on site.
Photos and videos from the site showed huge flames and smoke billowing in the sky even as firefighters tried to contain the blaze.
“Huge explosions, huge fireballs. People screaming and running everywhere for fear of more explosions,” an unidentified eye witness told Nation Africa.