Tokyo's Nikkei stock average ended down 0.91 percent on Monday as investors unloaded exporters such as Toyota Motor Corp. <7203.T> after renewed security concerns and higher oil prices cast a shadow over the outlook for the U.S. economy. The Nikkei <.N225> fell 103.54 points to 11,222.24, paring Friday's 1.88 percent gain. The broader TOPIX index <.TOPX> was off 0.32 percent at 1,135.64, with gains in shipping firms and utilities preventing the index from falling further.|||