Nikkei falls to 1-1/2-week low on Ukraine tensions; oil sector up

TOKYO, March 3 (Reuters) - Japan's Nikkei average slid to a 1-1/2-week low on Monday as escalating tensions in Ukraine sparked risk aversion and a stronger yen hurt the mood, but the oil sector bucked the trend after crude prices rallied to multi-month highs. The Nikkei ended 1.3 percent lower at 14,652.23, its lowest close since Feb. 20. The index extended losses into a fourth day. Ukraine mobilised for war on Sunday and Washington threatened to isolate Russia economically after Preside