South African Olympic runner Oscar Pistorius will face two additional gun-related charges when he goes on trial for murder next year, a spokesman for South Africa's National Prosecuting Authority said.

The charges will be heard alongside the murder charge when Pistorius' trial begins in March, Nathi Mncube told CNN.

Pistorius, nicknamed the "Blade Runner" for the special prostheses he uses for sprinting, has admitted to shooting dead his model girlfriend, Reeva Steenkamp, in his high-end home on Valentine's Day. But he has said it was an accident.

The gun-related charges are not new but have been moved from the South Gauteng jurisdiction where they were filed to the jurisdiction where the murder trial is being held, North Gauteng.

Pistorius is accused of two separate instances of firing a gun in a public space.

The National Prosecuting Authority decided to transfer them so that "all charges against Pistorius can be heard at the same place at the same time in front of the same judge," Mncube said.

The state has indicted the track star on a premeditated murder charge and, if convicted, he faces a mandatory sentence of life in prison.

Legal analysts in South Africa say they think the prosecution will seek to characterize Pistorius as a trigger-happy, irresponsible gun owner.

However, this apparent strategy could backfire if the gun-related charges made it seem less likely that Pistorius shot Steenkamp deliberately, said Kelly Phelps, a CNN legal analyst and lecturer in the law faculty of the University of Cape Town.

The alleged gun-related offenses, which will be prosecuted under South Africa's Firearms Control Act, date back to before the death of Steenkamp, but were not previously acted on.

The fact the National Prosecuting Authority is pursuing the charges now adds weight to the idea that prosecutors are seeking to create a negative "character picture" of Pistorius, Phelps said.

Pistorius, a double amputee, denies the murder charge and has said he mistook his girlfriend for a home invader when he fired shots from a pistol through a bathroom door that the 29-year-old was behind.

A spokeswoman for Pistorius said this month that he's hired an American forensic team to give expert testimony to cast doubt on evidence against him.

CNN's Brent Swails reported in Johannesburg and Laura Smith-Spark wrote and reported in London.