The theft of 70 military hand grenades at Hammanskraal, north of Pretoria, was confirmed by the manufacturer on Tuesday.

Rheinmetall Denel Munition (RDM) said the grenades were taken from a company vehicle at a filling station on the N1 early in the morning.

"From what we understand, the driver was at the station when he saw several assailants robbing a truck in front of him," RDM CEO Norbert Schulze said.

"After robbing that truck, those assailants then came to them (the driver and his assistant) and forcefully gained entry in the security-tight bakkie. They then fled with the goods."

The thieves made off with three crates each containing 35 grenades. Police found one of the crates in a nearby field.

The unmarked vehicle had been making its way from the Western Cape to the Wallmansthal Military Base, north of Pretoria.

Schulze said the missing military grenades were not as dangerous as conventional hand grenades.

"These (pyrotechnic) grenades simply illuminate when ignited and do not cause explosions like other grenades."

The worst it could do was burn someone who did not handle the grenade correctly. RDM said it was working with police and military officials in an attempt to recover the stolen goods.

Police spokesman Colonel Lungelo Dlamini could not immediately comment.