Eskom implemented rolling blackouts across the country on Tuesday as an ongoing protest over wages curbed electricity generation.

“Load shedding will continue on a rotational basis and will be implemented across the country,” the company said in an e-mailed statement. The reduction of 1GW will be from 5pm until about 10pm, it said.

The decision to introduce rolling blackouts is due to the “illegal strike action, which has severely impacted” Eskom’s power stations, spokesman Khulu Phasiwe said on Twitter. Generation units have been forced offline due to intimidation of staff and suspected acts of sabotage, he said.

Loss-making Eskom, which loses money despite generating more than 90% of the country’s electricity, has been flagged by ratings companies as a key risk to South Africa’s economy as it grapples with issues from insipid demand to unsustainable debt. Workers are protesting Eskom’s refusal to pay performance bonuses.

Police were called in Monday after at least four units were affected at sites including Koeberg, the nation’s only nuclear plant, according to Eskom. At the Matla plant, a conveyor belt typically used to feed coal, was cut, in what management suspected could be an act of sabotage. Coal trucking at some plants also stopped, creating shortages of the fuel, the utility said.

The National Union of Mineworkers, which represents the most employees of any labour group at Eskom, “participated in a peaceful protest” over Eskom’s refusal to pay a bonus and wasn’t responsible for sabotage, spokesman Livhuwani Mammburu said by phone.

Eskom offered to raise wages by as much as 7.5% annually after it was forced to introduce rolling blackouts last month when protesters blocked roads and attacked staff as wage talks broke down.

R2.3-billion loss

Still, the utility has stood firm on its refusal to pay bonuses, after reporting an annual loss of R2.3-billion last week. That stance amounts to an “act of war”, according to NUM. Legally, workers aren’t permitted to strike because the power producer is deemed to provide an essential service.

Management hasn’t determined whether the outage at the country’s only nuclear plant — a technical fault in one of the units that’s not in a sensitive area — is connected to the protest, Phasiwe said. Still, ramping up a nuclear unit can take days and a coal-powered equivalent up to eight hours, he said.

Eskom said last week that no bonus provision was raised as the utility missed its net profit target of R500-million. It also said financial constraints require a reduction in employee-benefit costs to keep the business sustainable.