"The number of people who died after a fuel tanker caught fire in Maridi town on Wednesday has exceeded 150," John Ezkia, Maridi county's executive director, was quoted by South Sudan's Eye Radio as saying.
"Our situation here in Maridi is not good," he said, pointing out that most of the injured people are women and children, Xinhua reported.
He added that other badly burned bodies have also been found around the wreckage of the tanker.
On Thursday, Information Minister Charles Kisagna of Western Equatoria, one of the 10 states of the country, said over 100 people were killed and about 50 others injured in South Sudan when an oil tanker swerved and exploded.
The minister noted that "those people may not survive because we do not have the facilities to treat the highly burnt people".
The oil tanker was going from the South Sudanese capital Juba to Yambio in Western Equatoria but it broke down near Maridi, where people flocked around it to scoop up the spilled fuel when it exploded.
Local sources were reported to have said that over 60 people were burnt to death at the scene, including women and children, noting that five brothers were among the dead.
Chandi Savior, the medical director of Maridi Civil Hospital, earlier said the hospital desperately needs more supplies of basics such as IV fluids, oxygen cylinders, oxygen concentrators, anti-tetanus, and pain relievers.