JOHANNESBURG--South African gold mine workers on strike Wednesday appeared to soften their wage demands as more than half of the country's mines reported production disruptions.

Around 80,000 gold mine workers embarked on a strike Tuesday night as the sector's biggest mine union seeks to push companies to up their latest wage offer. The National Union of Mineworkers, which previously said it was demanding entry level wage increases of up to 60%, said it would now consider hikes of around 15%, the union spokesman Lesiba Seshoka said.

Gold miners join auto workers and some airport technicians who are also on strike as part of salary negotiations. It's the largest mine strike to hit South Africa since widespread labor unrest sparked a series of violent strikes in August 2012 after police shot and killed 34 platinum miners striking outside Johannesburg.

The wildcat strikes last year cost the mining industry 15.3 billion rand ($1.5 billion) in lost production, and protracted work stoppages this year could have a similar effect, companies and government warn. Mining accounts for 6% of the country's already sluggish gross domestic product.

The Chamber of Mines, which represents the country's biggest gold producers, said 16 out of 23 gold mines reported either a full work stoppage or worker turnout of less than 50% Wednesday morning. Mining companies have offered to raise salaries between 6% and 6.5%, in line with South Africa's 6.3% annual inflation rate.

Mining companies have warned that if wages are settled in the double digits more of the country's marginal mines could close. Gold Fields Ltd. estimates that half of South Africa's gold and platinum mines are operating at a loss or just breaking even.

Already mining companies are either in liquidation proceedings or are laying off workers. Largest platinum producer Anglo American Platinum Ltd. (AMS.JO) said it will go ahead dismissing 3,300 employees at its South African mines this month as it restructures the business.

Write to Devon Maylie at devon.maylie@wsj.com

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