Thousands of workers, disgruntled over low wages and changes to terms and conditions of employment, went on strike on Friday at companies owned by Walmart-led Massmart Holdings, a labour union said.

The South African Commercial Catering and Allied Workers Union (Saccawu), an affiliate of Cosatu, said the indefinite strike is expected to draw more than 18 000 members across the country.

“We expect all the members to join the strike,” said Saccawu spokesman Sithembele Tshwete, adding some workers started picketing outside some Massmart stores at 6am.

The union has said it had exhausted all efforts to resolve labour disputes with Massmart, which owns Game, Makro and Builders Warehouse stores, and was left with no option but to go on strike.

The disputes include a wage dispute at Builders, with unions demanding an increase of R500 but Massmart is only offering an increase of R320. The union is also disputing unilateral restructuring and changes to terms and conditions of employment, which includes imposing a 40-hour working week with no premiums.

The union also wants workers who lost jobs as a result of restructuring at general merchandise Game chain to be reinstated. Massmart has said it had identified alternative jobs for those workers.

Tshwete said there were no immediate plans for the union to resume talks with Massmart.

Massmart said the strike could cost striking workers up to 25% of their November wages, if the industrial action was to last for a week.

“It is difficult not to conclude that the … industrial action represents a Saccawu leadership power play that is not necessarily in the best interests of their members,” Massmart said.