The index has soared since November, gaining 80 percent in the past six months. But its fortunes turned around with a 7.3 percent drop last Thursday, a 3.2 percent drop on Monday and a 5.15 percent drop this Thursday.
The index settled at 13,589.03, losing 737.43 points, following Tuesday's gain of 1.2 percent and Wednesday's marginal advance of 0.1 percent.
The tumble began after U.S. Federal Reserve Chairman Ben Bernanke said in a question and answer period at a hearing on Capitol Hill that the quantitative easing program could be reduced in the coming months.
Currently, the Fed buys $85 billion per month in long-term treasuries and mortgage-backed securities.
Some analysts are saying the recently dramatic stock market gains are a bubble created by generous monetary policies that have allowed corporations to borrow cheaply, The New York Times reported Thursday.
The correction in Japan, with markets off more than 13 percent from a peak above 16,000, was a predictable development given "an extraordinarily fast rise in share prices," over the past month, government spokesman Yoshihide Suga said at a press conference.
"In that regard, it would be unnatural if adjustments did not occur. It is normal for share prices to undergo corrections even as they rise," he said.
Japan's stock market has also been riding what has been called an economic sugar high which began after Prime Minister Shinzo Abe was sworn into office pledging measures to stimulate the economy.
"The falling share prices point to the dangers that are inherent in Abenomics," Ryutaro Kono, chief economist for Japan at BNP Paribas said in a research note.
Abe's policies "at first triggered an asset bubble and brought about an economic euphoria," Kono said. "But the endgame is a higher risk of financial ruin, as current policies are pushed to the limit by a surge in long-term interest rates."
Stocks on Thursday were down in Australia, China, Hong Kong and Taiwan. In Europe, markets held on to gains.
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