TOKYO, OCT. 1 (MONDAY) -- The key barometer of the Tokyo Stock Exchange, the Nikkei Stock Average, fell below 20,000 points during trading today for the first time in more than three years, although it recovered slightly by today's close.

"It's really snowballing. Everything, all that's bad is just carrying over," a stock trader said.

The Nikkei Average of 225 issues had shed 1,167.02 points, or 5.56 percent, falling to 19,816.48 at 1:30 p.m. It then recovered and closed down 761.64 points at 20,221.86, a drop of 3.63 percent.

Officials at Nomura Securities, one of Japan's largest brokerages, said shares were last traded below 20,000 points in late January 1987.

In currency trading, the dollar fell slightly against the yen today.

The dollar opened at 137.85 yen, 0.20 yen lower than its Friday finish at 137.95. Ranging between 137.20 yen and 137.88 yen, it was quoted at 137.35 yen at the end of morning trading.

On the stock market, traders briefly bought the Nikkei average to cover short, or oversold, positions, said Kazuhiro Nomura, a trader with New Japan Securities Co.

But internal technical factors accentuated the selling mood and sent the market barometer tumbling over 700 points by the end of the morning session, he said.