Most of the victims died on the spot when the bus rear-ended the abandoned tanker, which burst into flames near Saeedabad, some 143 miles northeast of Karachi, police officer Faisal Mahmood said. The bus driver's vision was apparently impaired by heavy rains and a broken windshield wiper.

Among the dead were 12 children, Mahmood said.

"The injured have been sent to Liaquat National hospital in Hyderabad city," he added, many suffering serious burns.

Pakistan has the world's third highest death rate from road accidents. Reckless drivers, overcrowded vehicles and poor roads are usually blamed for the high number of fatalities.