JOHANNESBURG  - Workers have embarked on an illegal strike at a South African mine run by world number three bullion producer AngloGold Ashanti, a company spokesman said on Friday, signalling spreading labour unrest in the mining sector.

"The night shift embarked on an unprotected strike at Kopanang and the morning shift didn't go down either," company spokesman Alan Fine said.

Fine said the mine has 5 000 workers and the strikers had not yet communicated their demands to the company.

A spokesman for the National Union of Mineworkers said the strikers wanted a wage of R12 500 a month, mirroring demands at other mines. This is about triple the amount earned as basic pay at the bottom end of the wage scale.

The AngloGold disruption comes a day after thousands reported back for work at platinum producer Lonmin after a wage hike deal was reached to end six weeks of industrial action and protest in which 45 people died.

Lonmin said the wage settlement would add 14% to its wage bill from October 1, a huge strain on a company battling with an already shaky balance sheet and rising costs on other fronts.

Workers at the world's top platinum producer Anglo American Platinum and bullion producer Gold Fields are also on illegal strikes over pay.

South African Reserve Bank Governor Gill Marcus said she was concerned the Lonmin settlement could set a precedent for future wage demands across Africa's biggest economy, spurring broader inflation.