Eskom has warned of load shedding amid sporadic industrial action by workers who staged pickets at its facilities across the country on Monday.

The utility has been engaged in wage negotiations with trade unions for two months, reaching an impasse over bonus payments on Friday.

Eskom said plant operations were negatively impacted at several power stations due to acts of intimidation, sabotage and obstruction of access to workplaces.

The company’s spokesman Khulu Phasiwe said in a statement that Eskom had activated its emergency structures but "the risk of load shedding remains high".

"Customers are advised to plan on the assumption that load shedding will take place and are encouraged to check their load-shedding schedules on the Eskom and their municipal website," he added.

Eskom had to implement load shedding in June when workers embarked on unlawful strikes after it offered 0% wage increases.

The entity now faces a similar fate following unions’ rejection of its decision not to pay workers bonuses for the next three years.

Organised labour demanded 12% of workers’ annual salaries as bonuses.

The National Union of Mineworkers (NUM) said it was aware that its members and those belonging to the National Union of Metalworkers of SA engaged in pickets on Monday.

NUM spokesman Livhuwani Mammburu told Business Day that the workers were "fighting for their bonuses".

He dismissed Eskom’s claims that the workers were responsible for disruptions at its plants.

"Members were peacefully picketing and there was no sabotage and intimidation, they just want their bonuses to be paid," he said.

Eskom employees are categorised as essential service and cannot take part in strikes.

However, earlier this month NUM warned that it would permit its members to go on strike if Eskom did not give in to its demands, regardless of the consequences.