Standard Bank Group Ltd. (SBK.JO), Africa's largest lender by assets, Thursday said its first-half net profit fell 31% as loan impairments rose amid the global economic slump.

Net profit fell to 5.11 billion rand ($639 million) from ZAR7.4 billion a year earlier.

Basic earnings per share dropped 34.4% to 354.7 cents, from 540.5 cents. Standard Bank in late July forecast a 30%-35% decline in earnings per share, fleshing out a warning in May that it was unlikely to match the previous year's performance.

Still, net interest income was 15% higher on the year at ZAR16.52 billion and non-interest revenue was up 6% at ZAR15.28 billion.

Absa Group Ltd. (ASA.JO), South Africa's biggest retail lender, earlier this month said it expects to remain under pressure for the rest of the year due to rising arrears and non-performing loans. The bank, majority owned by the U.K.'s Barclays PLC (BCS), posted a 39% drop in its first-half net profit after impairments rose and business volumes fell.

Standard Bank's shares ended Wednesday at ZAR95.70, up about 15% since the start of the year and in line with a rise in Johannesburg's blue chip Top 40 index.

-By Robb M. Stewart, Dow Jones Newswires; +27 11 783 7848; robb.stewart@dowjones.com