At least five prisoners were killed and several more injured when a bomb tore through a prison transport van in Johannesburg, South African police and rescue services said.
In what appears to be a failed escape attempt, police said a door of the van was blown open as it transported 36 prisoners back to a jail in southern Johannesburg from a magistrate's court where they are awaiting trial.
"The driver heard a big bang. They noted there was a hole in the door and saw two prisoners escape," the South African Police Service said in a statement, adding that police then arrested the two.
Police were still investigating what kind of bomb was used, spokesman Brigadier Neville Malila told Talk Radio 702.
"The explosive device that was used is still unknown," he said.
Police told reporters at a news conference that three of prisoners were confirmed dead and 14 more injured. The remaining 19 were free from injury, police said.
However, an emergency services worker told Reuters that four prisoners had died at the scene and another died en route to hospital.
No bystanders appeared to have been injured in the explosion, which occurred near the jail.
Police said they were investigating charges of murder, possession of explosives and escape from lawful custody.
While gun violence is not unusual in South Africa, cases involving explosives tend to be rare.
