The Colombo Stock Exchange's main index dropped 0.5 percent, or 29.34 points, to close at 5,861.35, its lowest since Sept. 19.
Turnover was 565.5 million rupees ($4.37 million), half of this year's daily average of 962 million rupees.
The bourse saw a net foreign inflow of 16.1 million rupees, extending the net inflow so far this year to 32.32 billion rupees ($249.81 million).
The rupee closed a tad firmer at 129.10/20 a dollar, from Wednesday's close of 129.50/60 as the Bank of Ceylon sold dollars, dealers said.
($1 = 129.3750 Sri Lanka rupees)
(Reporting by Ranga Sirilal and Shihar Aneez; Editing by Sanjeev Miglani)
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