The inflation rate rose to 4.6% in May - the highest level this year - as the rand weakened and the effect of lower oil prices evaporated. Inflation accelerated from 4.5% in April, Statistics SA said yesterday. The median estimate of 23 economists surveyed earlier by Bloomberg was for it to remain constant at 4.5%.Prices rose 0.3% in the month.In a separate statement, Stats SA said retail sales grew 3.4% in April, compared with the median estimate of 2.1%.Though the central bank's monetary policy committee has left its benchmark interest rate unchanged at 5.75% since July - to support an economy that grew at its slowest pace last year since the 2009 recession - rising petrol, electricity and food costs are putting pressure on prices.The deputy governor of the Reserve Bank, Daniel Mminele, said recently interest rates could not remain unchanged indefinitely.Bart Stemmet, an economist at NKC African Economics, said: "Inflation is moving to the upper end of the central bank's target because petrol prices are rising and food prices are picking up."If Eskom's application to raise its tariffs by as much as 25% is approved, "it will push the Reserve Bank's inflation forecasts above the target band and force it to increase interest rates", he said.The Reserve Bank targets headline inflation of between 3% and 6%. The core inflation rate, which excludes food, non-alcoholic beverages, petrol and electricity costs, rose to 5.7% in May from 5.6% in the previous month.Growth in retail trade sales was much greater than expected in April, despite load-shedding and deteriorating consumer confidence. The main contributors were general dealers and retailers in textiles, clothing, footwear and leather goods. ..