UPDATE 1-Kenya shilling weakens, stocks close higher

* Main share index up for fourth straight session * Shilling eases due to importer, interbank demand By George Obulutsa NAIROBI, Feb 25 (Reuters) - The Kenyan shilling weakened slightly on Tuesday as importers and commercial banks bought dollars for end-of-month payments, while shares closed higher for the fourth straight session. At the close of trade at 1300 GMT, commercial banks quoted the shilling at 86.40/50 to the dollar, compared with Monday's close of 86.25/35.