Johannesburg - South African stocks posted a second straight session of gains on Monday led by the world's top platinum mining companies, which gained as palladium hit a 13-year high.

Impala Platinum, the world's second largest platinum producer, added 2.85 percent, making it the top blue-chip performer of the day, while bigger rival Anglo American Platinum climbed 2.25 percent to 472.37 rand.

Palladium, which both companies produce, scaled 13-year peaks above $900 (R9,567) an ounce on supply concerns from top producer Russia - a rare piece of positive news for the platinum group metals industry, which has been battling with depressed prices.

Bucking the upward trend, Capitec Bank shed almost 2.7 percent after a Moody's rating downgrade that cited concerns about the bank's exposure to risky consumer lending.

The ratings agency's move came after South Africa's central bank had to launch a $1.6 billion bailout of African Bank Investments (Abil), which ran into trouble as bad debts soared among its core market of low-income borrowers.

Some analysts questioned Moody's rationale, noting that Capitec was generally considered to have sounder lending practices and a better business model than its fallen rival.

“They are the only one left with significant exposure to that low-income market. But this Moody's downgrade might be overdone because two weeks ago there were no real concerns about Capitec though we all knew that Abil had problems,” said Christie Viljoen of NKC Independent Economists.

Shares of South Africa's No.2 drugmaker Adcock Ingram slid over 5 percent in late trade after the company flagged a loss in the first nine months of its fiscal year.

The benchmark Top-40 index added 0.68 percent to 46,424 while the wider All-share index climbed 0.61 percent to 51,572. - Reuters