MTN Group Ltd. workers in South Africa are set to go on strike after a breakdown in wage talks between Africa’s biggest mobile-phone company by subscribers and a key labor group.

The Communications Workers Union sent MTN an intention to strike and 120 protesters gathered outside the company’s Johannesburg offices, MTN spokeswoman Jacqui O’Sullivan said in an emailed response to questions Friday.

The dispute is over the extent of salary increases from April 1 this year, she said.

MTN’s operations are “largely unaffected,” O’Sullivan said .

The union move comes in the same week as MTN was forced to shut down offices in Nigeria over violent protests by labor groups. South Africa and Nigeria are two of the company’s three biggest markets.

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