Nathi Mncube, a spokesman for the National Prosecuting Authority, said the charges were related to Pistorius' alleged violations of firearms law, eNews Channel Africa reported.
Mncube, who said Pistorius was notified of the new charges Wednesday, said he was "not prepared to comment on the nature of the charges."
A section of the indictment charges the athlete on Feb. 16 "did unlawfully have in his possession ammunition, to wit 38 x 38 rounds, without being the holder of a license in respect of a firearm capable of discharging that ammunition."
Pistorius' trial in the death of his girlfriend, model Reena Steenkamp, on Feb. 14 is scheduled to begin March 3 in Pretoria.
Pistorius has acknowledged shooting and killing Steenkamp at his home after mistaking her for an intruder.