According to eNCA television news, one of the charges is linked to an event in January where Pistorius -- who is already accused of murdering his girlfriend -- accidentally fired a gun in an upmarket Johannesburg restaurant.
In another case, Pistorius allegedly discharged his gun out of the sunroof of a friend's car on their way back from a holiday.
The National Prosecuting Authority declined to confirm the additional charges, saying "everything would be revealed in court" at the pre-trial hearing on Monday.
He claims he shot Steenkamp through a locked bathroom door in the dead of night after he mistook her for an intruder.
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The state is arguing that the murder was premeditated. A date for the trial is expected to be set on Monday.
Pistorius has kept a low profile since his release on bail of one million rand (USD 101,000, 76,000 euros), a week after the killing.
The star who runs on two fibreglass prosthetic legs has also abandoned his professional running career.