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.

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.