* Sets aside R2.5 bln in general provisions
* NPLs higher than anticipated
* Lower sales at retail unit
* Shares down 13 pct (Adds analyst, details)
By Helen Nyambura-Mwaura
JOHANNESBURG, May 2 (Reuters) - African Bank Investments forecast a first-half loss of 3.3 billion rand ($315 million) on Friday, sending its shares down 13 percent after it surprised investors with the news it would have to set aside more money to cover bad debts.
The South African bank said it would have to increase its provisions for non-performing loans by some 2.5 billion rand after non-performing loans ballooned to 6 billion rand in the first half of the year - 600 million more than forecast.
Abil, as it is commonly known, is the country's biggest provider of unsecured loans to largely lower income customers. The bank will report first-half earnings later this month.
"It took everyone by surprise in terms of the loss of 3 billion plus. I don't think it was anticipated that they would take additional provisions after what they had done in the prior period," said Patrice Rassou, head of equities at Sanlam Investment Management.
Most South African banks have scaled back on risky but lucrative unsecured loans in the last few years. But for Abil micro-lending to low-income earners provides its primary income.
Many of its customers have been struggling in an economy where average household debt accounts for 75 percent of disposable income and one in four people have no work. Tens of thousands of platinum miners have also been on strike for over three months now in South Africa, exacerbating the difficulties of banks catering to low-income households.
The bank posted an 88 percent plunge in 2013 earnings after two previous profit warnings.
Most of Abil's troublesome loans were made before June 2013, after which the bank tightened its lending criteria. It also changed its policies to increase credit loss provisions and to write off bad loans sooner.
Abil said the higher provisions would aid a quicker recovery.
"This action is being taken to prevent future results from continuing to be adversely affected by the higher level of emergence of NPLs from the pre July 2013 business," it said.
The bank expects a headline loss per share of between 239 and 254 cents in the six months to end March, compared with restated headline earnings of 62.3 cents last year.
Abil said its furniture retail arm Ellerines booked a loss of up to 1.3 billion rand as customers scaled back on purchases. It is trying to sell the hire purchase unit to concentrate on purely lending and has started talks to be a secondary credit provider to customers of clothing retailer Edcon.
Absa, the South African unit of Barclays Africa Group , is Edcon's primary credit provider after buying the store's card portfolio in 2012. ($1 = 10.4830 South African Rand) (Editing by Sophie Walker)