GFI Gold Fields Ltd

JOHANNESBURG--AngloGold Ashanti Ltd. (AMS.JO) said workers have embarked on an illegal strike at its Kopanang mine, a further instance of unrest that is closing major gold and platinum mines across the country.

AngloGold said workers for the night and day shift didn't come to work. The mine accounts for about 4% of its total gold output and employs about 5,000 people.

The strike comes as four mines remain closed at Anglo American Platinum Ltd. and one at Gold Fields Ltd, where miners are demanding higher wages. The strike action started at Lonmin PLC last month when 3,000 rock drillers downed tools to demand a salary increase. This week Lonmin agreed to 11-22% pay increases, and many in the industry predicted the agreement could lead to further strike activity.

AngloGold said workers' demands haven't yet been submitted to the company.

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