Johannesburg - Numsa members working for arms manufacturer Denel have embarked on a protected strike, the union said on Friday.
National Union of Metalworkers of SA (Numsa) co-ordinator Steve Nhlapo said members downed tools on Wednesday over a wage dispute with Denel.
"Denel has failed to adhere to a collective bargaining agreement signed between the union and its senior management," he said in a statement.
"The action is an... attack and [a] well-engineered liquidation of our hard fought [for] collective bargaining system."
Denel spokesperson Sinah Phochana was not immediately available for comment.
Nhlapo said the union refused to allow its members to be "subjected to old apartheid wage disparities".
"We call on [the] Denel oligarchy to concede to these legitimate and genuine demands of workers," he said.
"Any dilly-dallying from Denel’s part [and] we will be forced to escalate our strike action until workers’ demands are addressed and resolved."