A female artillery officer risked her life on Friday in a desperate bid to prevent members of her battery dying from their own anti-aircraft gun.

But the brave, as yet unnamed officer was unable to stop the wildly swinging computerised Swiss/German Oerlikon 35mm MK5 anti-aircraft twin-barrelled gun. It sprayed hundreds of high-explosive 0,5kg 35mm cannon shells around the five-gun firing position.

By the time the gun had emptied its twin 250-round auto-loader magazines, nine soldiers were dead and 11 injured.

A ninth soldier, a woman, died moments after landing in Bloemfontein, after being airlifted by a South African Air Force helicopter to Pelonomi Hospital in Bloemfontein.

The accident occurred just before 9am when a battery from 10 Anti-Aircraft Regiment in Kimberley began a live-fire exercise at the Army Combat Training Centre at Lohatlha as part of the SANDF's Exercise Seboka - an annual joint conventional military exercise involving 5 000 soldiers from 18 army units, plus members of the SA Air Force, SA Navy and SA Military Health Service.

It is believed the soldiers were killed when the gun jammed moments after the exercise began.

When the female officer went forward to help the gunner clear the blockage, another shell was accidentally fired, causing some of the unspent ammunition in nearly-full magazines to explode.

This, in turn, caused a "runaway". There was nowhere to hide.

The rogue gun began firing wildly, spraying high-explosive shells at a rate of 550 a minute, swinging around through 360 degrees like a high-pressure hose.

The unknown officer tried to shut the gun down but she couldn't because the computer gremlin had taken over *1. Her fate was unknown at the time of going to press.

The injured, five of whom were female soldiers, were airlifted by SAAF choppers to various hospitals in Bloemfontein.

Three were in a critical condition last night.

Defence Ministry spokesperson Sam Mkhwanazi said the "friendly-fire" tragedy was the worst he could remember.

"Without hesitation I can say it is very rare; I can't even think of one - I can't remember when last an accident of this magnitude happened."

Many of the gunners were volunteers, having joined the defence force through its military skills development programme.

SANDF spokesperson Brigadier-General Kwena Mangope said Exercise Seboka was aimed at preparing troops for battle.

"It is assumed that there was a mechanical problem, which led to the accident.

"The gun, which was fully loaded, did not fire as it normally should have," he said.

"It appears as though the gun, which is computerised, jammed before there was some sort of explosion and then it opened fire uncontrollably, killing and injuring the soldiers."

He said the South African Police Service and the military police had begun an investigation to determine the cause of the accident. Preparations for a top-level board of inquiry involving the military, police and the government were well under way last night.

"Defence Minister Mosiuoa Lekota and SANDF chief General Godfrey Ngwenya have extended their sincerest sympathies and condolences to the families of the dead and injured," Mangope said.

He declined to divulge the names of the dead or injured until their next of kin had been informed.

Last night, welfare officers were counselling the traumatised survivors and their colleagues, while the chaplain service was informing the next of kin.

The general officer commanding the Army's Air Defence Artillery (ADA), Brigadier-General Stephen Marumo, could not be reached for comment.

The SANDF is in the middle of a R3-billion programme to upgrade its ADA, adding gunner-toted short-range missile systems, longer-range vehicle-mounted systems and a new fire-control system.

Jane's defence analyst Helmoed-Römer Heitman said the last military accident of this magnitude was the accidental ramming and sinking of the frigate SAS President Kruger in 1982, in which 16 sailors were killed.

* This article was originally published on page 1 of The Star on October 13, 2007

With acknowledgements to Graeme Hosken, Michael Schmidt and Johan du Plessis and Independent Online.

Condolences are extended to all those killed, injured and affected by this tragedy.

*1 As an electronics engineer, it is difficult for me to contemplate a control system failure mode that could lead to unintentional firing of a continuous burst until the ammunition is expended.

When we worked on Projects Dart and Catchy, which had a Oerlikon 35 mm Mk5 twin-barrelled anti-aircraft cannon as their weapons, even though the fire control system was automatic, a gunner still had to sit on the weapon, keep a target in the standard optical sight and keep a finger depressed on the manual trigger (or was this a firing pedal?).

It is trite system engineering practice that such a system should fail to a safe mode.

But if this tragic accident was caused by faulty system design, faulty electronic hardware or faulty software then the engineers and company which effected the such design and implementation need to be outed.

What I do also know, is that the few dozen Oerlikon 35 mm Mk5 twin-barrelled anti-aircraft cannons acquired by the SADF from Switzerland in the 1980s or early 1990s were not fully automatic and local developments took place to provide them with automatic fire control systems (including, I think, electric gun drives).