State-owned power utility Eskom resumed rolling blackouts Friday after protesting employees blocked others from working and interfered with the electricity grid.

Eskom, which generates almost all of the nation’s electricity, is locked in a dispute with workers after wage talks broke down last week over the utility’s insistence that it can’t afford pay increases. The company cut power to some areas on Thursday night for the first time since 2015 as demonstrators blockaded roads and attacked staff.

Eskom will implement rolling blackouts from 11.30am to 9pm “due to multiple trips of its power generation units”, spokesman Khulu Phasiwe said on Twitter. “Acts of intimidation and sabotage continue today at some of Eskom’s power stations, a move that has begun to threaten the security of power supply,” he said a few minutes earlier.

The situation is likely to remain “severely constrained” until the wage dispute is resolved, Phasiwe said by phone.

The utility got a court order declaring the protests unlawful and prohibiting the intimidation of other workers and contractors. Employees are also barred from hijacking coal trucks and sabotaging Eskom’s electricity infrastructure.

Members of Eskom’s biggest unions plan to picket during their break midday on Friday, when the activity is allowed, Livhuwani Mammburu, a spokesman for the National Union of Mineworkers, said by phone. Legally, workers are not permitted to strike because the power producer is considered to provide an essential service.

The unions are waiting to hear from the Commission for Conciliation, Mediation and Arbitration about the next steps after the dispute was referred to mediation, Mammburu said.

“We are not on strike,” Phakamile Hlubi, a spokeswoman for the National Union of Metalworkers of South Africa, said late on Thursday. The unions delivered a memorandum to Eskom headquarters earlier in the day demanding a 15% salary increase. — Reported by Ntando Thukwana and Paul Burkhardt, with assistance from Alastair Reed, (c) 2018 Bloomberg LP