TOKYO, Oct 25 (Reuters) - Japan's Nikkei stock average suffered the biggest one-day loss in 2-1/2 months on Friday, hit by yen's strength against the dollar and as fears grew that tight credit conditions in China could put the brakes on the world's second-largest economy. The Nikkei shed 2.8 percent to 14,088.19, its lowest closing level since Oct. 9. For the week, the benchmark fell 3.3 percent, marking its first weekly fall in three weeks. The broader Topix dropped 2.1 percent to 1,178.28 in relatively thin trade, with 2.41 billion shares changing hands. At one point during the session, the dollar weakened to a low of 96.94 against the yen.