Striking truck drivers aligned to the SA Transport Allied Workers Union (Satawu) are not responsible for the acts of violence that marred the week long industrial action, the union said on Saturday.
"We have thus far realised that none... of our members are party to all [the] reported cases of crime that have seen the attack of fellow workers and torching as well as damaging of private property," spokesperson Vincent Masoga said in a statement.
He blamed the violence on criminals who wanted to tarnish the union's reputation.
"Those who seek to destroy our progressive image and are hell bent on criminal and thuggish behaviour, continue to opportunistically hijack our just cause to further their malicious acts and practices," Masoga said.
He said all unions involved in the wage dispute with the Road Freight Employers Association (RFEA) condemned the violence.
He urged striking workers to maintain "iron discipline" and to not succumb to acts of intimidation and attacks during the strike.
"We will co-operate with the law enforcement agencies to ensure that we root out all forms of attacks, intimidation and criminal activities that seek to taint the noble industrial action we are currently leading."
On Friday, in Pinetown, Durban, about 50 striking truck drivers set a truck on fire on Henwood Road, eThekwini metro police said.
Superintendent Eugene Msomi said the truck driver ran away when he was stopped by the strikers.
On Wednesday, a truck was stoned by protesters in Kempton Park, Ekurhuleni emergency services said.
Spokesperson William Ntladi said in Germiston, on the M2 and Refinery Road, protesters stopped a truck with three occupants. Two assistants to the truck driver were hospitalised after being assaulted by the protesters.
The truck was set alight.
The African Christian Democratic Party on Saturday condemned the violence.
Gauteng ACDP leader Lydia Meshoe said workers who were practising their right to strike should not intimidate others who chose to work.
"No truck driver who takes seriously his or her duty to support dependants and unemployed family members deserves to be called a 'rat' and to risk a half-brick through the windscreen at intersections," she said.
Meshoe said government should hold unions responsible for acts of violence and intimidation during strikes.
Workers in the freight transport sector are on strike over wages.
Their unions have reverted to a 12 percent pay demand after rejecting a lower offer tabled by employers on Tuesday.
On Friday, the Labour Court granted an interdict prohibiting violence by striking workers.
The RFEA had approached the court due to the escalation in violence and intimidation experienced since the strike started.
The court interdicted unions and their members from obstructing public roads or interfering with traffic, and obstructing entrances or exits to any workplace or related premises unless authorised by picketing rules.
It also interdicted unions from damaging any property including cars, committing any act of intimidation, violence and the carrying of any weapons.