The reception area of the Johannesburg Stock Exchange. File picture: Leon Nicholas

Johannesburg - South African stocks were on the back foot on Thursday, dragged lower by platinum miners after the world's second-biggest producer Impala posted a sharp fall in earnings in the aftermath of a five-month strike.

Impala Platinum posted a 74 percent drop in full-year earnings and warned of a tough time ahead on the cost front as it struggles to ramp up production and implement wage increases of up to 20 percent.

Other platinum mining companies, Anglo American Platinum and Lonmin, lost 2.1 and 2.9 percent respectively.

Impala shares dropped the most on South Africa's Top-40 index, falling more than 5 percent to 97 rand.

The benchmark index lost more than 1 percent to 45,840 while the wider All-share index was down 0.9 percent to 51,133.

High-end food and clothing retailer Woolworths was among the risers, gaining 2 percent to 79.06 rand, after posting a 18 percent increase in underlying full-year profit.

The results bucked the trend of some other retailers such as Massmart Holdings, which reported a 25 percent tumble in first-half profit, reflecting the knock-on effect from the waves of strikes earlier this year.

Massmart shares shed nearly 2 percent.

Activity was relatively robust with 182 million shares traded with decliners outpacing advancers 159 to 134 companies. - Reuters