At least 121 people have been injured, of which the condition of at least five is described as critical.
The fire started last Friday evening when lightning struck an oil tanker. The fire has spread to another oil tank and caused several explosions. 17 firefighters who participated in the extinguishing work are missing, according to the authorities.
Cuba has asked for help and advice in the extinguishing work from friendly countries with experience in the oil sector, said a statement from the presidential office.
Around 1,900 people have been evacuated from areas near the oil storage. Satellite images from the scene show a thick plume of black smoke stretching west as far as the capital, Havana, ten miles away.