Johannesburg, Jul 11 (IANS): South African President Cyril Ramaphosa has called for calm after some people looted shops and burnt trucks calling for the release of former leader Jacob Zuma.

"President Ramaphosa says the impact of public violence against the road freight industry and damage to freeways that serve as economic arteries will be felt also by the people organiz=sing and committing these crimes. The President says the reasons allegedly advanced for the violence in KwaZulu-Natal cannot be used to legitimise vandalism and public violence," acting spokesperson in the Presidency, Tyrone Seale said on Saturday.

People burnt trucks and tyres on the N3, N2 and M7 and other key roads around the incarceration of the former President who was given 15-month sentence after defying the Constitutional Court's order which compelled him to appear and give evidence at the state capture commission in February, reports Xinhua news agency.

The South African police have arrested more than 20 suspects for violent protest which resulted in at least 25 trucks being torched in KwaZulu-Natal.

On Friday the "Free Zuma" group blocked roads, burning cars and attacking motorists calling for the former President's release.

The police on Saturday said they have beefed up deployment to contain the protests.

"A large number of people have already been arrested for incidents of criminality witnessed in the province yesterday and cases have been registered to trace and arrest those that still have to be arrested.

"A number of incidents were witnessed today of people who are opportunistic and used today's protest to enrich themselves by looting shops and other businesses," said KwaZulu-Natal police spokesperson Jay Naicker.

He stated that they will arrest those doing illegal gathering, not observing curfew regulations and looting shops.

Naicker said they have deployed police officers across the province to deal with protests.