The blast occurred on Friday evening in Odukpani in Cross River state in Nigeria's southeast.
“The number of victims is high,” but “I can't confirm the exact number,” said Cross River State Police spokeswoman Irene Ugbo.
One resident, Akpan Imon, said that at least 18 people died. “I counted 18 bodies, including those of burned women and children who were burnt beyond recognition,” he said.
“I think the toll could be higher because people from neighboring communities flocked to the scene of the accident,” he added.
According to another resident, Sunday Ibor, “more than 20 bodies” were removed”.
The wounded were evacuated to the University of Calabar hospital for burns of varying degrees.
Tanker truck and pipeline explosions are frequent in Nigeria, where the majority of the population lives in poverty despite the fact that the country is the continent's largest oil producer, with nearly 2 million barrels a day.
Fires and explosions often occur when people try to siphon oil from pipelines or when tankers overturn on the country's poorly maintained roads.
It was not immediately clear what caused the truck to overturn.
About a year ago, more than 30 residents in the same locality were burned to death while scooping fuel from an oil tanker involved in an accident.
Nigeria's worst such accident occurred in 1998, when more than 1,000 people died as the leaking oil pipeline from which they were scooping fuel exploded in the town of Jesse.