CONCERNS that major Japanese banks would release weak half-year earnings results today sent Tokyo stocks tumbling yesterday to an eight-month low. Futures-led selling accelerated price falls in the last 30 minutes and the Nikkei average briefly breached the 17,000-point level before closing at 17,067.11 - down 317.73 points or 1.83 per cent. ''We basically just ran out of time, and that's the only reason the market didn't go lower,'' said Frank Nelson, vice-president of equity derivatives at Lehman Brothers. It was the first time the Nikkei has fallen below 17,000 points since March 5, when it ended at 16,817.7. The market was closed on Tuesday for a national holiday. The shares slump prodded Bank of Japan governor Yasushi Mieno to say the central bank was watching the movement of stock prices ''with great interest''. He said share price movements were not normally a policy target for the central bank, but it intended to continue monitoring economic indicators including share prices, as price movements were reflecting the trend of worsening profits. Mr Mieno said the central bank saw ''no clear sign'' of economic recovery, but he did not rule out recovery before the end of March next year. However, traders said the market outlook for the next few weeks remained grim.