South Africa has deployed the army in four of its provinces on Friday after at least 21 trucks carrying goods were set on fire on national roads in various parts of the country over the past week.

Authorities have not established the motive for the attacks but Police Minister Bheki Cele said there is a possibility of economic sabotage against South Africa. He did not say who might be behind the campaign but police are hunting for at least 12 people believed to be linked to the attacks.

“These are organised and sophisticated operations,” Cele said in a statement released by the South African government’s official news agency.

Cele said there was no evidence that the truck burning was connected to the week-long violence and unrest in July 2021, when more than 350 people were killed and businesses were looted in a wave of protests sparked by the jailing of former President Jacob Zuma for contempt of court.

That case was back in the headlines on Thursday when South Africa’s apex Constitutional Court upheld a ruling that Zuma’s early release from prison on medical parole was improper and he should serve the remaining 13 months of his 15-month sentence. South Africa braced itself on Friday for more violent unrest over the decision.

The Department of Corrections has not said if it will order Zuma back to jail or if the time he spent on medical parole will count as him having served his sentence. South African media reports said the 81-year-old former president was in Russia receiving medical treatment for an undisclosed illness.

Soldiers were deployed in the northern provinces of Limpopo and Mpumalanga, the eastern province of KwaZulu-Natal where Zuma is from, and the central province of Free State. The army would support police in their response to the truck attacks, the South African Department of Defence said.

Cele said 21 trucks had been burned down since Sunday in the Limpopo, Mpumalanga, and KwaZulu-Natal provinces. Sunday, when the truck burning apparently started, was the second anniversary of the start of the 2021 violence.

“No matter the motive, the country’s law enforcement remains on high alert and is hard at work at preventing more attacks but also finding these individuals or gangs of thugs who are hell-bent on causing havoc on our roads,” Cele said.

Authorities have not reported any deaths or serious injuries related to the torching of trucks.