91 percent (61.85 points) to 6,721.54, while the more liquid Milanka index fell back below the 6,000 mark, sliding 0.81 percent (49.02 points) to close at 5,982.95, according to stock exchange figures.
Turnover was 1.96 billion rupees.
Newly listed Capital Alliance Finance was the most actively traded stock and highest gainer, closing at 39.90 rupees, up 24.90 or 166 percent, having opened at its reference price of 15 rupees, an indicative price decided by the company.
Almost 13.6 million shares of Capital Alliance Finance were traded with the stock hitting a day's high of 50 rupees and accounting for the day's highest turnover.
There were several crossings or off-market private deals of Capital Alliance Finance all at 30 rupees a share.
Regnis (Lanka), whose price had risen shaply in speculative trade, closed at 455.10 rupees, down 33.70 or 6.89 percent, ending a 12-day winning streak, analysts said.
The share opened at 500 rupees, and hit a high of 505 and a low of 420, with 777,600 shares done. It accounted for the second highest turnover.
Analysts said the share had risen almost 180 percent from 175 rupees on September 14, 2011 to 488.80 on October 3.
Colonial Motors closed at 488.90 rupees, down 2.90, with one crossing of 50,000 shares at 480 rupees a share.
"The bourse dropped heavily today on account of the broad levels of selling," Lanka Securities said in a report.
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"Regnis (Lanka) witnessed a high level of volatility during the day.
"The counter rallied to a high of 505 rupees in the morning and in the mid-trading session jittery investors realized gains with high level of selling."
Meanwhile, the Colombo Stock Exchange said in a statement the bourse continues to "reinforce its position" among the regional markets, with the All Share Price Index showing a positive performance compared with regional exchanges.
"Globally, most stock exchanges have recorded negative growth as measured by their respective broad market indices which track the market price movements," it said.