An explosion at an illegal oil refinery in southern Nigeria has killed at least 80 people, the emergency services said on Sunday.

The explosion occurred late Friday at the illegal site between the southern oil states of Rivers and Imo, police said.

"We recovered at least 80 badly burnt bodies at the scene," Ifeanyi Nnaji of the National Emergency Management Agency (NEMA) in the area, told AFP, adding that the toll could rise further.

"We learnt many bodies are in nearby bushes and forests as some illegal operators and their patrons scampered for safety."

Nnaji said that several burnt vehicles and jerry-cans used in scooping stolen crude and petroleum products littered the scene.

The incident Friday is the latest to hit oil-rich Nigeria in recent years.

According to local media reports, more than 100 people were killed in the blast.

Illegal crude refining is common in the southern-oil region where thieves vandalize pipelines to steal crude which they refine to sell on the black market.

Most people in the oil-producing Niger delta live in poverty even though the country is the biggest oil producer on the continent, with output of around two million barrels per day.