NAIROBI, Aug 7 (Reuters) - The Kenyan shilling firmed through the psychological level of 84.00 per dollar on Tuesday, helped by aid agencies and exporters selling greenbacks in the absence of demand from importers. At 0717 GMT, commercial banks quoted the shilling at 83.90/84.10 per dollar, stronger than Monday's close of 84.00/20, and showing signs of breaking out of a a 84.00-84.50 range in which it has been hemmed in for over four weeks. "We've seen some inflows from development agencies and usual exporters. There is also a slow down in demand (for dollars)," said Dickson Magecha, a trader at Standard Chartered Bank. "The support now is at 83.80, but if we break that we will be in new territory." The shilling has gained 1.4 percent against the dollar this year, helped by the central bank keeping a tight rein on monetary policy after sharp rises in interest rates last year to prop up the currency and fight inflation. Rising central bank foreign exchange reserves, which have grown to above the statutory four months of import cover, have also given the bank the muscle to intervene in markets when necessary.

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