The main stock index fell to 2.03 percent before closing down 1.87 percent, or 136.78 points, at 7,184.22, its lowest since Sept. 17. It hit a near 3-1/2 year closing high on Oct. 3.
"It's a free fall. Today the fall is led by banking and large-cap shares," said Dimantha Mathew, manager, research at First Capital Equities (Pvt) Ltd.
First Capital Research in a note to investors said it expects selling pressure to continue for the next few days mainly stemming from large-cap counters.
Biggest listed lender Commercial Bank of Ceylon Plc , which led the overall fall, lost 5.92 percent to 157.30 rupees, while DFCC Bank Plc shed 6.27 percent to 215.40 rupees.
The day's turnover was 1.97 billion rupees ($15.09 million), more than this year's daily average of 1.36 billion rupees.
Foreign investors bought 284.1 million rupees worth of shares on Monday after three straight sessions of outflows. The bourse has enjoyed a net foreign inflow of 9.45 billion rupees year-to-date, exchange data showed.
The market saw 526.9 million rupees ($4 million) worth of foreign selling in stocks during the last three sessions through Friday.
($1 = 130.5500 Sri Lankan rupee) (Reporting by Ranga Sirilal and Shihar Aneez; Editing by Sunil Nair)
http://www.reuters.com/article/2014/10/13/markets-sri-lanka-stocks-close-idUSL3N0S83G920141013