The South African presidency announced on Saturday the deployment of the military to guard the country's electricity plants.
Blackouts have become routine in Africa's most industrialised nation but further cuts imposed recently by state-owned company Eskom have generated anger.
According to President Cyril Ramaphosa's spokesman, the move was "in response to the growing threat of sabotage, theft, vandalism and corruption" at coal and diesel-powered plants.
The cuts have cost the economy hundreds of millions of dollars in lost output as well as disrupting trade and industry.
Earlier this week Eskom CEO Andre de Ruyter announced his resignation, citing crime and corruption as the main obstacles he faced to turn around the troubled state-owned company.